Ccna guide
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This document provides an overview and table of contents for a book titled "CCNA Practice Questions (Exam 640-802) Third Edition" by Jeremy Cioara. The book contains practice questions and answers to help readers study and prepare for the CCNA certification exam. It is divided into two parts that cover the ICND1 and ICND2 exam objectives. Each part contains multiple chapters that review topics like networking fundamentals, routing, switching, WAN technologies and network security. The document lists the chapter titles and topics covered in each one to help readers understand the scope of the material in the book.
![• Key topics: This indicates important figures, tables, and lists of information
that you need to know for the exam. They are sprinkled throughout each
chapter and are summarized in table format at the end of each chapter.
• Memory tables: These can be found on the DVD within Appendices C and
D. Use them to help memorize important information.
• Key terms: Key terms without definitions are listed at the end of each
chapter. Write down the definition of each term, and check your work against
the complete key terms in the Glossary.
For current information about the CompTIA Network+ certification exam, you
can
visithttp://certification.comptia.org/getCertified/certifications/network.aspx.
Who Should Read This Book?
The CompTIA Network+ exam measures the necessary competencies for an
entry-level networking professional with the equivalent knowledge of at least
500 hours of hands-on experience in the lab or field. This book was written for
people who have that amount of experience working with computer networks.
Average readers will have connected a computer to a network, configured IP
addressing on that computer, installed software on that computer, used
command-line utilities (for example, the ping command), and used a browser
to connect to the Internet.
Readers will range from people who are attempting to attain a position in the
IT field to people who want to keep their skills sharp or perhaps retain their
job because of a company policy that mandates they take the new exams.
This book also targets the reader who wants to acquire additional
certifications beyond the Network+ certification (for example, the Cisco
Certified Network Associate [CCNA] certification and beyond). The book is
designed in such a way to offer easy transition to future certification studies.
Strategies for Exam Preparation
Strategies for exam preparation vary, depending on your existing skills,
knowledge, and equipment available. Of course, the ideal exam preparation
would include building and configuring a computer network from scratch.
Preferably, the network would contain both Microsoft Windows® and UNIX
hosts, at least two Ethernet switches, and at least two routers.
However, not everyone has access to this equipment, so the next best step you
can take is to read the chapters in this book, jotting down notes with key
concepts or configurations on a separate notepad. For more visual learners,
you might consider the Network+ Video Mentor product by Anthony Sequeira,
which is available from Pearson IT Certification, where you get to watch an
expert perform multiple configurations.
After you read the book, you can download the current exam objectives by
submitting a form on the following web](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-91-320.jpg)
![• WAN link: Today, most networks connect to one or more other networks.
For example, if your company has two locations, and those two locations are
interconnected (perhaps via a Frame Relay or Multiprotocol Label Switching
[MPLS] network), the link that interconnects those networks is typically
referred to as a wide-area network (WAN) link. WANs, and technologies
supporting WANs, are covered in Chapter 7, ―Introducing Wide-Area
Networks.‖
Networks Defined by Geography
As you might be sensing at this point, not all networks look the same. They
vary in numerous ways. One criterion by which we can classify networks is
how geographically dispersed the networks components are. For example, a
network might interconnect devices within an office, or a network might
interconnect a database at a corporate headquarters location with a remote
sales office located on the opposite side of the globe.
Based on the geographical dispersion of network components, networks can
be classified into various categories, including the following:
• Local-area network (LAN)
• Wide-area network (WAN)
• Campus-area network (CAN)
• Metropolitan-area network (MAN)
• Personal-area network (PAN)
The following sections describe these different classifications of networks in
more detail.
LAN
A LAN interconnects network components within a local region (for example,
within a building). Examples of common LAN technologies you’re likely to
encounter include Ethernet (that is, IEEE 802.3) and wireless networks (that
is, IEEE 802.11). Figure 1-2 illustrates an example of a LAN.
Figure 1-2 Sample LAN Topology](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-101-320.jpg)
![d. Peer-to-server
10. Which of the following is an advantage of a peer-to-peer network, as
compared with a client-server network?
a. More scalable
b. Less expensive
c. Better performance
d. Simplified administration
Chapter 2. Dissecting the OSI Model
After completion of this chapter, you will be able to answer the following
questions:
• What is the purpose of a network model?
• What are the layers of the OSI model?
• What are the characteristics of each layer of the OSI model?
• How does the TCP/IP stack compare to the OSI model?
• What are the well-known TCP and/or UDP port numbers for a given
collection of common applications?
Way back in 1977, the International Organization for Standardization (ISO)
developed a subcommittee to focus on the interoperability of multivendor
communications systems. What sprang from this subcommittee was the Open
Systems Interconnection (OSI) reference model (commonly referred to as
the OSI model or the OSI stack). With this model, you can take just about any
networking technology and categorize that technology as residing at one or
more of the seven layers of the model.
This chapter defines those seven layers and provides examples of what you
might find at each layer. Finally, this chapter contrasts the OSI model with
another model (the TCP/IP stack, also known as the Department of
Defense [DoD]model), which focuses on Internet Protocol (IP)
communications.
Foundation Topics: The Purpose of Reference Models
Throughout your networking career, and throughout this book, you will
encounter various protocols and devices that play a role in your network. To
better understand how a particular technology fits in, however, it helps to have
a common point of reference against which various technologies from various
vendors can be compared.
One of the most common ways of categorizing the function of a network
technology is to state at what layer (or layers) of the OSI model that
technology operates. Based on how that technology performs a certain
function at a certain layer of the OSI model, you can better determine if one
device is going to be able to communicate with another device, which might or](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-121-320.jpg)
![popular in the mid 1990s) was the IPX/SPX stack of protocols. However, most
modern Novell networks rely on TCP/IP rather than IPX/SPX.
Note
Microsoft introduced its own implementation of Novell’s IPX/SPX, which was
named NWLink IPX/SPX.
Just as Layer 2 and Layer 3 each offer flow control services, flow control
services also exist at Layer 4. Two common flow control approaches at Layer 4
are as follows:
• Windowing: TCP communication uses windowing, in that one or more
segments are sent at one time, and a receiver can acknowledge the receipt of
all the segments in a window with a single acknowledgment. In some cases, as
illustrated in Figure 2-11, TCP uses a sliding window, where the window size
begins with one segment. If there is a successful acknowledgment of that one
segment (that is, the receiver sends an acknowledgment asking for the next
segment), the window size doubles to two segments. Upon successful receipt
of those two segments, the next window contains four segments. This
exponential increase in window size continues until the receiver does not
acknowledge successful receipt of all segments within a certain time period
(known as the round trip time [RTT], which is sometimes called real transfer
time), or until a configured maximum window size is reached.
Figure 2-11 TCP Sliding Window](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-134-320.jpg)
![Figure 1-4. Three different networks
Solution:
For LAN A, a CIDR block that can handle at least 300 networking devices
must be provided. In this case, two contiguous Class C networks of
192.168.0.0/24 and 192.168.1.0/24 can be grouped together to form a
192.168.0.0/23 network. Referring to Table 1-2, a /23 CIDR with a subnet
mask of 255.255.254.0 provides 512 IP addresses which more than satisfies
the required 300 networking devices.
The next question is to determine what the network address is for LAN A. This
can be determined by ANDing the 255.255.254.0 subnet mask with
192.168.0.0 and 192.168.1.0.
This shows that applying the /23 [255.255.254.0] subnet mask to the specified
IP address places both in the same 192.168.0.0 network. This also means that
this CIDR block does not cross boundaries, because applying the subnet mask
to each network address places both in the same 192.168.0.0 network.
For LAN B1, the requirement is that a CIDR block that can handle 800
network devices must be provided. According to Table 1-2, a /22 CIDR yields
1,022 usable host IP addresses and is equivalent to grouping four Class C
networks together. Therefore, a /22 CIDR can be used.
The next decision is selecting the group of IP addresses to create the CIDR
block and decide where the IP addresses should start. Recall that the
192.168.0.0 and 192.168.1.0 networks are being used to create the LAN A](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-188-320.jpg)
![VLAN has its own broadcast domain. Hence, traffic from one VLAN cannot
pass to another VLAN. The advantage of using VLANs is the network
administrator can group computers and servers in the same VLAN based on
the organizational group (such as Sales, Engineering) even if they are not on
the same physical segment—or even the same building.
VLAN (Virtual LAN)
A group of host computers and servers that are configured as if they are in the
same LAN, even if they reside across routers in separate LANs.
There are three types of VLANs: port-based VLANs, tag-based VLANs,
andprotocol-based VLANs. The port-based VLAN is one where the host
computers connected to specific ports on a switch are assigned to a specific
VLAN. For example, assume the computers connected to switch ports 2, 3,
and 4 are assigned to the Sales VLAN 2, while the computers connected to
switch ports 6, 7, and 8 are assigned to the Engineering VLAN 3, as shown
in Figure 1-7. The switch will be configured as a port-based VLAN so that the
groups of ports [2,3,4] are assigned to the sales VLAN while ports [6,7,8]
belong to the Engineering VLAN. The devices assigned to the same VLAN will
share broadcasts for that LAN; however, computers that are connected to
ports not assigned to the VLAN will not share the broadcasts. For example, the
computers in VLAN 2 (Sales) share the same broadcast domain and
computers in VLAN 3 (Engineering) share a different broadcast domain.
Figure 1-7. An example of the grouping for port-based VLANs
Port-Based VLAN
Host computers connected to specific ports on a switch are assigned to a
specific VLAN.
Tagged-Based VLAN
Used VLAN ID based on 802.1Q.
Protocol-Based VLAN
Connection to ports is based on the protocol being used.](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-194-320.jpg)
![that a VLAN must be created for it to be activated and ready for use. The steps
for creating the VLAN on newer Cisco switches are as follows:
Click here to view code image
SwitchA# conf t
SwitchA(config)#vlan 2
SwitchA(config-vlan)#name Sales
SwitchA(config-vlan)#vlan 3
SwitchA(config-vlan)#name Engineering
SwitchA(config-vlan)#exit
SwitchA(config)#exit
To start configuring a VLAN, one must specify which VLAN needs to be
configured using the vlan [vlan_id] command. If the specific VLAN does not
exist, this command will create the VLAN as well. As shown in the preceding
example, the command vlan 2 is entered to configure vlan 2 and then the
command name Sales is entered to configure the name associated to the
VLAN. The similar steps are done for VLAN 3 with the name Engineering.
vlan [vlan_id]
The IOS global command used to create VLAN ID.
The rest of the VLAN commands are almost identical in the older switches and
newer switches. The next step is used to verify that the new VLANs have been
created using the show vlan command:
Click here to view code image
Switch#show vlan
VLAN Name Status Ports
---- -------------------------- --------- -----------------------------
1 default active Fa0/1, Fa0/2, Fa0/3,
Fa0/4
Fa0/5, Fa0/6,
Fa0/7, Fa0/8
Fa0/9, Fa0/10
2 Sales active
3 Engineering active
This shows that both the Sales and Engineering VLANs have been created. In
the next steps, ports will be assigned to the newly created VLANs. This
requires that the configuration mode be entered and each FastEthernet
interface (port) must be assigned to the proper VLAN using the two
commands switchport mode access and switchport access vlan vlan-id.
An example is presented for FastEthernet interface 0/2 being assigned to
VLAN 2 on a Cisco switch:
Click here to view code image
SwitchA#conf t
Enter configuration commands, one per line. End with CNTL/Z.
SwitchA(config)#int fa 0/2
SwitchA(config-if)#switchport mode access
SwitchA(config-if)#switchport access vlan 2
SwitchA(config-if)#end](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-197-320.jpg)
![sequence demonstrates how to configure an interface port 24 on an HP switch
as a 802.1Q VLAN tagging port:
Click here to view code image
SwitchHP# conf
SwitchHP(config)# vlan 1
SwitchHP(vlan-1)# tagged 24
SwitchHP(vlan-1)# exit
SwitchHP(config)# vlan 2
SwitchHP(vlan-2)# tagged 24
SwitchHP(vlan-2)# exit
Unlike Cisco switches where an 802.1Q is configured at the interface level, the
tagging configuration is done at the VLAN level on HP switches. Port 24 is
designated as tagged port for both VLAN 1 and VLAN 2, which enables it to
carry VLAN 1 and VLAN 2 frames. Generally, untagged ports belong to one
specific VLAN, while tagged ports can belong to one or more VLANs.
1-4. Routed Network
This section examines the Layer 3 network and how data is routed in the
network. This section also introduces another Layer 3 device, the multilayer
switch. You need to understand the advantages and disadvantages of this
device. This section also introduces interVLAN configuration, which enables
VLANs to communicate across networks. The section concludes with a look at
both serial and ATM configurations. Some network engineers will argue that
the serial and ATM technologies are a dying technology and are now
considered obsolete. However, being obsolete does not mean they are
nonexistent. These technologies are still being used throughout the world, and
it is still an important topic.
Router
The router is a powerful networking device used to interconnect LANs. The
router is a Layer 3 device in the OSI model, which means the router uses
thenetwork address (Layer 3 addressing) to make routing decisions
regarding forwarding data packets. In the OSI model, the Layer 3, or network,
layer responsibilities include handling of the network address. The network
address is also called a logical address, rather than being a physical address
(such as the MAC address, which is embedded into the network interface card
[NIC]). Thelogical address describes the IP address location of the network
and the address location of the host in the network.
Network Address
Another name for the Layer 3 address.
Logical Address
This describes the IP address location of the network and the address location
of the host in the network.](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-207-320.jpg)
![Synchronous Optical Network (SONET)
Used to interconnect the router and the network to other WANs.
WAN
Wide-area network.
Routed Port Configuration
Routers can have Ethernet (10 Mbps), Fast Ethernet (100 Mbps), Gigabit
Ethernet (1,000 Mbps), and 10 gigabit (10 GB), Serial, and ATM interfaces.
These routers can have multiple interfaces, and the steps for configuring each
interface are basically the same. Each interface is assigned a number. For
example, a router could have three FastEthernet interfaces identified as
FastEthernet 0/0
FastEthernet 0/1
FastEthernet 0/2
The notation 0/0 indicates the [interface-card-slot/port].
On Cisco’s routers, a routed port can be configured simply by assigning an IP
address to the interface. Once an IP address and its subnet mask are assigned
to the interface and the interface is enabled, a Layer 3 network is created. The
interface IP address becomes the gateway for that network. To program the
interface, the router must be in the configuration mode. The following
demonstrates how to configure a router’s FastEthernet 0/0 port (FastEthernet
0/0, also listed as fa0/0 and FA0/0) as a routed interface.
Click here to view code image
Router(config)# int fa0/0
Router(config-if)# ip address 10.10.20.250 255.255.255.0
Router(config-if)#no shut
2w0d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0,
changed state to up
Notice that the router prompts you that the line protocol on interface
FastEthernet 0/0 changed state to up. These log messages are always
displayed when connecting via the console port. However, they are suppressed
when it is a remote terminal session, like Telnet or SSH. To display log
messages on the remote terminal, issue the command terminal
monitor or term mon at the router prompt:
terminal monitor (term mon)
Displays log messages on the remote terminal.
Router# term mon
The log messages can be useful when bringing up a new connection.
Sometimes, they can be annoying if the router is logging too many events. To
disable the logging to the terminal, the command is terminal no](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-214-320.jpg)
![Secondary IP addresses can be useful when you want to add more networks
without having to disturb the existing network or to use it as a transitional
network for network migration. Some people might just want to run multiple
logical subnets on one physical subnet. To add a secondary IP address to the
interface, the command isip address [ip_address]
[subnet_mask] secondary. The keyword secondaryis used to specify the
secondary IP address. The secondary IP address configuration is as follows:
Click here to view code image
Router(config)# interface FastEthernet0/0
Router(config-if)# ip address 10.10.20.250 255.255.255.0
Router(config-if)# ip address 172.16.1.1 255.255.255.0 secondary
Secondary IP Address
Allows multiple Layer 3 networks to reside on the same physical link.
In order to configure the secondary IP address, the primary IP address must
exist first. There can be as many secondary IP addresses as needed. The
secondary IP address cannot be verified with the show int or show ip int
brief command. The results will only display the primary IP address
information.
InterVLAN Routing Configuration
As previously discussed in Section 1-3, ―VLAN Network,‖ each VLAN is its own
broadcast domain. It cannot forward traffic across its VLAN boundaries.
However, it is almost impractical in today’s applications for a VLAN not to be
able to communicate beyond itself. To enable communications among
VLANs,InterVLAN routing is required.
InterVLAN routing
Enables communications among VLANs.
router on a stick
Eliminates connecting a link from each VLAN to a router port by utilizing a
trunk or 802.1Q port.
The most logical solution to route traffic between different VLANs is to
introduce or create a Layer 3 routed network between them. One traditional
way is to connect each VLAN to a router interface. Then, each router interface
is configured as a different Layer 3 network. This enables VLANs to
communicate and pass traffic via the Layer 3 IP network. For a few VLANs,
this does not present an issue, but for a large number of VLANs, this could
create some issues. This means that every VLAN will require a physical
connection to a router port. Router ports are expensive, and this design can be
costly as the number of VLANs increases and more physical links are required.](https://image.slidesharecdn.com/ccnaguide-130312020142-phpapp01/85/Ccna-guide-216-320.jpg)
Ccna guide
- 1. Exam Cram CCNA Practice Questions (Exam 640-802) Third Edition Jeremy Cora, CCIE No. 11727
- 2. Contents at a Glance Part I: ICND1 CHAPTER 1: Operation of Data Networks CHAPTER 2: Switching Foundations CHAPTER 3: Basic IP Services CHAPTER 4: IOS and Routing Foundations CHAPTER 5: Wireless and Network Security Concepts CHAPTER 6: Basic WAN Connectivity Part II: ICND2 CHAPTER 7: Advanced Switching Concepts CHAPTER 8: Subnetting, VLSM, and IPv6 CHAPTER 9: Advanced Routing Configuration CHAPTER 10: Access Lists and Network Address Translation CHAPTER 11: Frame Relay, PPP, and VPN Connectivity APPENDIX: What's on the CD-ROM Table of Contents About the Author Introduction Part I: ICND1 Chapter 1: Operation of Data Networks Quick Answer Key Answers and Explanations Chapter 2: Switching Foundations Quick Answer Key Answers and Explanations Chapter 3: Basic IP Services Quick Answer Key Answers and Explanations Chapter 4: IOS and Routing Foundations Quick Answer Key Answers and Explanations Chapter 5: Wireless and Network Security Concepts Quick Answer Key Answers and Explanations Chapter 6: Basic WAN Connectivity Quick Answer Key Answers and Explanations Part II: ICND2
- 3. Chapter 7: Advanced Switching Concepts Quick Answer Key Answers and Explanations Chapter 8: Subnetting, VLSM, and IPv6 Quick Answer Key Answers and Explanations Chapter 9: Advanced Routing Configuration Quick Answer Key Answers and Explanations Chapter 10: Access Lists and Network Address Translation Quick Answer Key Answers and Explanations Chapter 11: Frame Relay, PPP, and VPN Connectivity Quick Answer Key Answers and Explanations Appendix: What's on the CD-ROM Multiple Test Modes Attention to Exam Objectives Installing the CD Creating a Shortcut to the MeasureUp Practice Tests Technical Support About the Author Jeremy Cioara, CCIE No. 11727, Part I: ICND1 Chapter 1 Operation of Data Networks Chapter 2 Switching Foundations Chapter 3 Basic IP Services Chapter 4 IOS and Routing Foundations Chapter 5 Wireless and Network Security Concepts Chapter 6 Basic WAN Connectivity Chapter 1. Operation of Data Networks
- 4. This chapter covers the following CCNA objectives that fall under the content area, Describe how a network works: Describe the purpose and functions of various network devices. Select the components required to meet a network specification. Use the OSI and TCP/IP models and their associated protocols to explain how data flows in a network. Describe common networked applications including web applications. Describe the purpose and basic operation of the protocols in the OSI and TCP models. Describe the impact of applications (Voice over IP and Video over IP) on a network. Interpret network diagrams. Determine the path between two hosts across a network. Describe the components required for network and Internet communications. Identify and correct common network problems at Layers 1, 2, 3, and 7 using a layered model approach. Differentiate between LAN/WAN operation and features. 1. You are a network technician at Bubbles, Inc. Your newly appointed trainee is troubleshooting a connectivity problem on the network and would like to test application layer connectivity between devices. What command would you use? 1. A. ping 2. B. telnet 3. C. traceroute 4. D. verify 5. E. trace Quick Answer: 16 Detailed Answer: 17 2. You are connecting a laptop to a Cisco router to configure it for the first time. After opening your terminal program and selecting COM1, you are prompted for the port settings. What settings should you use? 1. A. 9600bps, 8 data bits, no parity, 1 stop bit, hardware flow control 2. B. 9600bps, 8 data bits, no parity, 1 stop bit, no flow control 3. C. 56000bps, 8 data bits, no parity, 1 stop bit, hardware flow control 4. D. 56000bps, 8 data bits, no parity, 1 stop bit, no flow control
- 5. Quick Answer: 16 Detailed Answer: 17 3. Which of the following is a security concern when configuring a device using Telnet? 1. A. All communication is sent in clear text. 2. B. Passwords are sent using reversible encryption. 3. C. Passwords cannot be changed in a Telnet session. 4. D. Passwords are not used during a Telnet session. Quick Answer: 16 Detailed Answer: 17 4. You are attempting to test telnet connectivity to a Cisco router in your company's lab environment, but are unable to create a session. What should you do to resolve the problem? 1. A. Use a straight-through cable to connect your computer's COM port to the router's console port. 2. B. Use a rollover cable to connect your computer's COM port to the router's console port. 3. C. Use a straight-through cable to connect your computer's COM port to the router's Ethernet port. 4. D. Use a crossover cable to connect your computer's Ethernet port to the router's Ethernet port. 5. E. Use a rollover cable to connect your computer's Ethernet port to the router's Ethernet port. 6. F. Use a straight-through cable to connect your computer's Ethernet port to the router's Ethernet port. Quick Answer: 16 Detailed Answer: 17 5. Which of the following is a valid benefit of using a hub in an enterprise network? 1. A. A network hub could be used to monitor network traffic from multiple sources using a packet sniffer or IDS/IPS appliance. 2. B. Because it is hardware-based, a hub can transmit traffic with less latency than a network switch. 3. C. A hub provides a better throughput for steady, low-bandwidth streams of traffic such as Voice over IP (VoIP) or Video over IP (VIP). 4. D. A hub provides dedicated bandwidth on a per-port basis. Quick Answer: 16 Detailed Answer: 17
- 6. 6. You are preparing to discuss the foundations of network communication with a junior administrator at your company. How would you describe the characteristics of TFTP using the OSI model? 1. A. TFTP is a transport layer protocol that transmits using TCP port 21. 2. B. TFTP is an application layer protocol that transmits over the transport layer protocol TCP using port 21. 3. C. TFTP is an application layer protocol that transmits over the transport layer protocol UDP using port 69. 4. D. TFTP is a network layer protocol that transmits using UDP port 69. Quick Answer: 16 Detailed Answer: 17 7. You are using Microsoft Internet Explorer on a PC to access the Cisco website (www.cisco.com). What source port will your PC use for communication? 1. A. UDP port 80. 2. B. TCP port 80. 3. C. The port will be randomly assigned by the operating system. 4. D. Any TCP port under 1024. Quick Answer: 16 Detailed Answer: 17 8. You are a network consultant for a small, 20-user company. The company has purchased a new building and would like you to design a network infrastructure using Cisco equipment. The company will be using a cable modem Internet connection, multiple mobile laptops, and 15 stationary desktop PCs. The company would also like VPN connectivity remotely to the office. What are the most likely network components you will use? (Choose three.) 1. A. Cisco switch 2. B. Cisco router 3. C. VLANs 4. D. ASA firewall 5. E. Cisco Wireless Access Point 6. F. Cisco IPS Sensor Quick Answer: 16 Detailed Answer: 18 9. An interface capable of sending at a T1 speed would be transmitting data at which of the following? 1. A. 1.544 Mbps
- 7. 2. B. 1.544 MBps 3. C. 1.544 Gbps 4. D. 1.544 GBps Quick Answer: 16 Detailed Answer: 18 10. Routing decisions are made at which layer of the OSI model? 1. A. Application 2. B. Transport 3. C. Session 4. D. Data Link 5. E. Network Quick Answer: 16 Detailed Answer: 18 11. Which of the following protocols operate solely at Layer 2 of the OSI model? (Choose three.) 1. A. 802.3 MAC 2. B. IP 3. C. HDLC 4. D. PPP 5. E. ISDN 6. F. TCP Quick Answer: 16 Detailed Answer: 18 12. Which of the following are common network applications? (Choose three.) 1. A. Graphics creation 2. B. Email 3. C. Spreadsheets 4. D. Instant messaging 5. E. Database 6. F. Word processing Quick Answer: 16 Detailed Answer: 18 13. What is the primary purpose of a router? (Choose two.) 1. A. To provide an intermediary device where network signals are transmitted
- 8. from one device to another 2. B. To control broadcast and multicast traffic from flooding through multiple networks 3. C. To interconnect networks and provide the best path between them 4. D. To protect networks using firewall capabilities implemented by using access lists Quick Answer: 16 Detailed Answer: 18 14. Refer to Figure 1.1. HostA wants to communicate with ServerB. What destination MAC address will be in the header of the packet at position A (as notated in Figure 1.1)? Figure 1.1. Network diagram. 1. A. The MAC address of HostA 2. B. The MAC address of SwitchA 3. C. The MAC address of RouterA 4. D. The MAC address of RouterB 5. E. The MAC address of SwitchB 6. F. The MAC address of ServerB Quick Answer: 16 Detailed Answer: 18 15. Refer to Figure 1.1. HostA wants to communicate with ServerB. What destination IP address will be in the header of the packet at position A (as notated in Figure 1.1)? 1. A. The IP address of HostA 2. B. The IP address of SwitchA 3. C. The IP address of RouterA 4. D. The IP address of RouterB
- 9. 5. E. The IP address of SwitchB 6. F. The IP address of ServerB Quick Answer: 16 Detailed Answer: 19 16. Refer to Figure 1.1. HostA wants to communicate with ServerB. What source MAC address will be in the header of the packet at position B (as notated in Figure 1.1)? 1. A. The MAC address of HostA 2. B. The MAC address of SwitchA 3. C. The MAC address of RouterA 4. D. The MAC address of RouterB 5. E. The MAC address of SwitchB 6. F. The MAC address of ServerB Quick Answer: 16 Detailed Answer: 19 17. Refer to Figure 1.2. HostA is unable to communicate with ServerB. Based on the information given in the Figure 1.2, what is the most likely cause of the problem? Figure 1.2. Network diagram. 1. A. HostA and ServerB are on different subnets. 2. B. HostA and ServerB are on the same subnet. 3. C. RouterA or RouterB has an access list, which prevents HostA from reaching ServerB. 4. D. Crossover cables should be replaced with straight-through cables. Quick Answer: 16 Detailed Answer: 19
- 10. 18. Which of the following are valid fields in a TCP header? (Choose four.) 1. A. Sequence number 2. B. Source IP address 3. C. Checksum 4. D. Acknowledgement number 5. E. Destination MAC address 6. F. Destination port Quick Answer: 16 Detailed Answer: 19 19. Refer to Figure 1.3. HostA issues a ping request to HostB. Which of the following outputs would accuratelyreflect the contents of the ARP table on HostA? Figure 1.3. Network diagram. 1. A. C:> arp -a Interface: 192. 168. 1.10 on Interface 0x10000003 Internet Address Physical Address Type 192.168.1.1 00-0c-85-4c-05-00 dynamic 2. B. C:> arp -a Interface: 192. 168. 1.10 on Interface 0x10000003 Internet Address Physical Address Type
- 11. 192.168.1.1 00-0c-85-4c-05-00 dynamic 192.168.2.1 00-0c-85-4c-05-01 dynamic 192.168.2.10 00-b1-33-df-5e-11 dynamic 1. C. C:> arp -a Interface: 192 .168. 1.10 on Interface 0x10000003 Internet Address Physical Address Type 192.168.1.1 00-0c-85-4c-05-00 dynamic 192.168.2.10 00-b1-33-df-5e-11 dynamic 2. D. C:> arp -a Interface: 192. 168. 1.10 on Interface 0x10000003 Internet Address Physical Address Type 192. 168. 1.11 00-0a-11-3c-34-01 dynamic Quick Answer: 16 Detailed Answer: 19 20. You are troubleshooting network connectivity issues between a Microsoft Windows client and a server. The server's IP address recently changed and you want to clear the client's ARP table. What command will accomplish this? 1. A. arp -clear 2. B. arp -a 3. C. arp –c all 4. D. arp –d * Quick Answer: 16 Detailed Answer: 19 21. Which of the following commands would allow a network client to test connectivity to a destination device and verify the current delay for each router traversed while making the connection? 1. A. ping 2. B. test 3. C. tracert 4. D. telnet 5. E. ssh –h -d Quick Answer: 16 Detailed Answer: 19
- 12. 22. Refer to Figure 1.4. HostA just transmitted a certain amount of data to HostB. What does HostB's response indicate? Figure 1.4. Network diagram. 1. A. HostB's response is a retransmission of data requested by HostA. 2. B. HostB has indicated that a portion of HostA's transmission was not received and needs to be retransmitted. 3. C. HostB's response indicates the TCP session will now close. 4. D. HostB's response is normal and expected. Network communication will continue unhindered. Quick Answer: 16 Detailed Answer: 20 23. The following is a list of network functions. Enter the appropriate letter to match the network function to the corresponding OSI layer. A = Data link layer B = Network layer 1. A. ______Provides error detection 2. B. ______Routes data packets 3. C. ______Finds the best path to use when delivering data 4. D. ______Provides logical addressing 5. E. ______Provides physical addressing 6. F. ______Defines how data is formatted for transmission Quick Answer: 16 Detailed Answer: 20 24. Match the correct term to the corresponding OSI layer. A = Physical layer B = Data link layer C = Network layer D = Transport layer
- 13. 1. A. ______ Segments 2. B. ______ Frames 3. C. ______ Bits 4. D. ______ Packets Quick Answer: 16 Detailed Answer: 20 25. The application layer of the TCP/IP stack corresponds to which of the following three OSI model layers? (Choose three.) 1. A. ______ Physical 2. B. ______ Transport 3. C. ______ Data link 4. D. ______ Segments 5. E. ______ Presentation 6. F. ______ Session 7. G. ______ Network 8. H. ______ Application Quick Answer: 16 Detailed Answer: 21 26. A host is assigned the IP address 10.5.62.173/27. An application on the host attempts to contact a server with the IP address 10.5.62.158/27. What is the next step in the process of network communication? 1. A. The host will send an ARP message directly to the destination server to obtain its MAC address. 2. B. The host will contact the IP address of its default gateway to find the MAC address for the destination server. 3. C. The host will send an ARP broadcast to find the MAC address of its default gateway. 4. D. The host will send an ARP broadcast to find the MAC address of the destination server. Quick Answer: 16 Detailed Answer: 21 27. Users on a specific network segment in your organization are complaining that they cannot reach the Internet. While working through the troubleshooting process, you discover that all the ports connecting to the PCs in the segment have been set to auto-negotiate speed and duplex. You also gather information from one of the end-user workstations; this information is shown in Figure 1.5. What is the most likely cause of the problem?
- 14. Figure 1.5. Command prompt output. 1. A. All host and server connections in the network should have speed and duplex hard coded. 2. B. The connectivity problems are related to an IP addressing issue. 3. C. The default gateway could be blocking ICMP ping traffic. 4. D. All ports should be set for 10Mbps, half-duplex connections for testing purposes. Quick Answer: 16 Detailed Answer: 22 28. Refer to Figure 1.6. HostA has just sent a ping request to HostB. Based on the information given in Figure 1.6, how will the switch respond? Figure 1.6. Network diagram.
- 15. 1. A. The switch will forward the frame out FA0/2. 2. B. The switch will flood the frame out all ports. 3. C. The switch will multicast the frame only to unknown ports. 4. D. The switch will flood the frame out all ports except FA0/1. Quick Answer: 16 Detailed Answer: 22 Share 29. When data is being encapsulated, the last piece of information to be added is the _________. 1. A. TCP source and destination port 2. B. Destination IP address 3. C. Source IP address 4. D. FCS
- 17. About This Book How to Use This Book How This Book Is Organized Book I: Networking Basics Book II: Building a Network Book III: Network Administration and Security Book IV: TCP/IP and the Internet Book V: Wireless Networking Book VI: Mobile Networking Book VII: Windows Server 2008 R2 Reference Book VIII: Using Other Windows Servers Book IX: Managing Linux Systems Icons Used in This Book Where to Go from Here Book I Chapter 1: Understanding Networks What Is a Network? Network building blocks Why bother? Of Clients and Servers Dedicated Servers and Peers Networks Big and Small Network Topology Bus topology Star topology Expanding stars Ring topology Mesh topology Chapter 2: Understanding Network Protocols and Standards Understanding Protocols Understanding Standards The Seven Layers of the OSI Reference Model The Physical Layer The Data Link Layer The Network Layer The Transport Layer The Session Layer The Presentation Layer The Application Layer Following a Packet through the Layers The Ethernet Protocol Standard Ethernet
- 18. Fast Ethernet Gigabit Ethernet The TCP/IP Protocol Suite IP TCP UDP Other Protocols Worth Knowing About Chapter 3: Understanding Network Hardware Servers What's important in a server Components of a server computer Server form factors Network Interface Cards Network Cable Coaxial cable Twisted-pair cable Switches Repeaters Bridges Routers Network Attached Storage Network Printers Chapter 4: Understanding Network Operating Systems Network Operating System Features Network support File-sharing services Multitasking Directory services Security services Microsoft's Server Operating Systems Windows 2000 Server Windows Server 2003 Windows Server 2008 Windows Server 2008 R2 Other Server Operating Systems Linux Apple Mac OS/X Server Novell NetWare Peer-to-Peer Networking with Windows Advantages of peer-to-peer networks Drawbacks of peer-to-peer networks Windows 7
- 19. Windows Vista Older Windows versions Book II Chapter 1: Planning a Network Making a Network Plan Being Purposeful Taking Stock What you need to know Programs that gather information for you To Dedicate or Not to Dedicate: That Is the Question Types of Servers File servers Print servers Web servers Mail servers Database servers Choosing a Server Operating System Planning the Infrastructure Drawing Diagrams Sample Network Plans Building a small network: California Sport Surface, Inc. Connecting two networks: Creative Course Development, Inc. Improving network performance: DCH Accounting Chapter 2: Installing Network Hardware Installing a Network Interface Card Installing Twisted-Pair Cable Cable categories What's with the pairs? To shield or not to shield When to use plenum cable Sometimes solid, sometimes stranded Installation guidelines Getting the tools that you need Pinouts for twisted-pair cables Attaching RJ-45 connectors Crossover cables Wall jacks and patch panels Installing Coaxial Cable Attaching a BNC Connector to Coaxial Cable Installing Switches Daisy-Chaining Switches Chapter 3: Setting Up a Network Server
- 20. The Many Ways to Install a Network Operating System Full install versus upgrade Installing over the network Automated and remote installations Gathering Your Stuff A capable server computer The server operating system Other software A working Internet connection A good book Making Informed Decisions Final Preparations Installing a Network Operating System Phase 1: Collecting Information Phase 2: Installing Windows Configuring Your Server Chapter 4: Configuring Windows Clients Configuring Network Connections Configuring Windows XP network connections Configuring Windows Vista network connections Configuring Windows 7 network connections Configuring Client Computer Identification Configuring Windows XP computer identification Configuring Windows Vista or Windows 7 computer identification Configuring Network Logon Chapter 5: Macintosh Networking What You Need to Know to Hook Up a Macintosh Network Mac networking protocols Mac OS X Server What You Need to Know to Use a Macintosh Network Configuring a Mac for networking Accessing a network printer Sharing files with other users Accessing shared files What You Need to Know to Network Macintoshes with PCs Chapter 6: Configuring Other Network Features Configuring Network Printers Adding a network printer Accessing a network printer using a Web interface Configuring Internet Access Configuring clients for DHCP
- 21. Using Internet Connection Sharing Mapping Network Drives Chapter 7: Verifying Your Network Installation Is the Computer Connected to the Network? Is the Network Configuration Working? Can the Computers Ping Each Other? Can You Log On? Are Network Drives Mapped Correctly? Do Network Printers Work? Chapter 8: Going Virtual Understanding Virtualization Looking at the Benefits of Virtualization Getting Started with Virtualization Creating a Virtual Machine Book III Chapter 1: Help Wanted: Job Description for a Network Administrator Knowing What Network Administrators Do Choosing the Part-Time Administrator Establishing Routine Chores Managing Network Users Patching Up Your Operating System and Software Discovering Software Tools for Network Administrators Building a Library Getting Certified CompTIA Microsoft Cisco Gurus Need Gurus, Too Helpful Bluffs and Excuses Chapter 2: Security 101 Do You Need Security? Considering Two Approaches to Security Physical Security: Locking Your Doors Securing User Accounts Obfuscating your usernames Using passwords wisely A Password Generator For Dummies Securing the Administrator account Hardening Your Network Using a firewall Disabling unnecessary services
- 22. Patching your servers Securing Your Users Chapter 3: Managing User Accounts Exploring What User Accounts Consist Of Looking at Built-In Accounts The Administrator account The Guest account Service accounts Assigning User Rights Controlling User Access with Permissions (Who Gets What) Assigning Permissions to Groups Understanding User Profiles Automating Tasks with Logon Scripts Chapter 4: Firewalls and Virus Protection Firewalls The Many Types of Firewalls Packet filtering Stateful packet inspection (SPI) Circuit-level gateway Application gateway The Built-In Windows Firewall Virus Protection What is a virus? Antivirus programs Safe computing Using Windows Action Center Chapter 5: Extending Your Network with VPN Access Understanding VPN Looking at VPN Security Understanding VPN Servers and Clients Chapter 6: Managing Network Software Understanding Software Licenses Using a License Server Options for Deploying Network Software Deploying software manually Running Setup from a network share Installing silently Creating an administrative installation image Pushing out software with group policy Keeping Software Up to Date Chapter 7: Solving Network Problems When Bad Things Happen to Good Computers
- 23. Fixing Dead Computers Ways to Check a Network Connection A Bunch of Error Messages Just Flew By! Double-Checking Your Network Settings Using the Windows Networking Troubleshooter Time to Experiment Who's on First? Restarting a Client Computer Booting in Safe Mode Using System Restore Restarting Network Services Restarting a Network Server Looking at Event Logs Documenting Your Trials and Tribulations Chapter 8: Network Performance Anxiety Why Administrators Hate Performance Problems What Exactly Is a Bottleneck? The Five Most Common Network Bottlenecks The hardware inside your servers The server's configuration options Servers that do too much The network infrastructure Malfunctioning components Tuning Your Network the Compulsive Way Monitoring Network Performance More Performance Tips Chapter 9: Backing Up Your Data Backing Up Your Data All about Tapes and Tape Drives Backup Software Types of Backups Normal backups Copy backups Daily backups Incremental backups Differential backups Local versus Network Backups How Many Sets of Backups Should You Keep? A Word about Tape Reliability About Cleaning the Heads Backup Security Chapter 10: Disaster Recovery and Business Continuity Planning
- 24. Assessing Different Types of Disasters Environmental disasters Deliberate disasters Disruption of services Equipment failure Other disasters Analyzing the Impact of a Disaster Developing a Business Continuity Plan Holding a Fire Drill Book IV Chapter 1: Introduction to TCP/IP and the Internet What Is the Internet? A Little Internet History TCP/IP Standards and RFCs The TCP/IP Protocol Framework Network Interface layer Network layer Transport layer Application layer Chapter 2: Understanding IP Addresses Understanding Binary Counting by ones Doing the logic thing Working with the binary Windows Calculator Introducing IP Addresses Networks and hosts The dotted-decimal dance Classifying IP Addresses Class A addresses Class B addresses Class C addresses Subnetting Subnets Subnet masks Network prefix notation Default subnets The great subnet roundup IP block parties Private and public addresses Network Address Translation Chapter 3: Using DHCP Understanding DHCP
- 25. Configuration information provided by DHCP DHCP servers How DHCP actually works Understanding Scopes Feeling excluded? Reservations suggested How long to lease? Working with a DHCP Server Installing and configuring a DHCP server Managing a DHCP server How to Configure a Windows DHCP Client Automatic Private IP Addressing Renewing and releasing leases Chapter 4: Using DNS Understanding DNS Names Domains and domain names Fully qualified domain names Top-Level Domains Generic domains Geographic domains The Hosts File Understanding DNS Servers and Zones Zones Primary and secondary servers Root servers Caching Understanding DNS Queries A real-life DNS example Zone Files and Resource Records SOA records NS records A records CNAME records PTR records MX records Reverse Lookup Zones Working with the Windows DNS Server How to Configure a Windows DNS Client Chapter 5: Using FTP Discovering FTP Configuring an FTP Server Installing FTP
- 26. Creating an FTP site Changing the FTP site properties Adding content to your FTP site Accessing an FTP Site with a Browser Using an FTP Command Line Client FTP Command and Subcommand Reference The FTP command ! (Escape) ? (Help) append ascii bell binary bye cd close debug delete dir disconnect get glob hash help lcd literal ls mdelete mdir mget mkdir mls mput open prompt put pwd quit quote recv remotehelp rename
- 27. rmdir send status trace type user verbose Chapter 6: TCP/IP Tools and Commands Using the arp Command Using the hostname Command Using the ipconfig Command Displaying basic IP configuration Displaying detailed configuration information Renewing an IP lease Releasing an IP lease Flushing the local DNS cache Using the nbtstat Command Using the netdiag Utility Using the netstat Command Displaying connections Displaying interface statistics Using the nslookup Command Looking up an IP address Using nslookup subcommands Displaying DNS records Locating the mail server for an e-mail address Taking a ride through DNS-Land Using the pathping Command Using the ping Command Using the route Command Displaying the routing table Modifying the routing table Using the tracert Command Book V Chapter 1: Setting Up a Wireless Network Diving into Wireless Networking A Little High School Electronics Waves and frequencies Wavelength and antennas Spectrums and the FCC Eight-Oh-Two-Dot-Eleventy Something? (Or, Understanding Wireless Standards)
- 28. Home on the Range Wireless Network Adapters Wireless Access Points Infrastructure mode Multifunction WAPs Roaming Wireless bridging Ad-hoc networks Configuring a Wireless Access Point Basic configuration options DHCP configuration Configuring Windows XP for Wireless Networking Using a Wireless Network with Windows XP Connecting to a Wireless Network with Windows Vista Connecting to a Wireless Network with Windows 7 Chapter 2: Securing a Wireless Network Understanding Wireless Security Threats Intruders Freeloaders Eavesdroppers Spoilers Rogue access points What About Wardrivers and Warchalkers? Wardriving Warchalking Securing Your Wireless Network Changing the password Securing the SSID Enabling WEP Using WPA Using MAC address filtering Placing your access points outside the firewall Chapter 3: Hotspotting What Is a Hotspot? What's So Great about Hotspots? Safe Hotspotting Free Hotspots Fee-Based Hotspots T-Mobile Boingo Setting Up Your Own Hotspot Chapter 4: Troubleshooting a Wireless Network
- 29. Checking for Obvious Problems Pinpointing the Problem Changing Channels Fiddle with the Antennas Adding Another Access Point Help! I Forgot My Router's Password! Chapter 5: Wireless Networking with Bluetooth Understanding Bluetooth Bluetooth Technical Stuff How to Add Bluetooth to Your Computer Using Bluetooth in Windows Installing a USB Bluetooth Adapter Enabling Discovery Installing a Bluetooth Mouse or Keyboard Book VI Chapter 1: Managing Mobile Devices The Many Types of Mobile Devices Considering Security for Mobile Devices Chapter 2: Managing BlackBerry Devices Understanding BlackBerry Adding a BES User Locking and Erasing a Handheld Chapter 3: Managing iPhone Devices Understanding the iPhone Integrating iPhone with Exchange Enabling Exchange Mobile Services Enabling ActiveSync for a user's mailbox Configuring the iPhone for Exchange e-mail Chapter 4: Managing Android Devices Understanding Android Phones Looking at the Android Operating System Perusing Android's Core Applications Integrating Android with Exchange Chapter 5: Managing Netbooks Understanding Netbook Computers Connecting with a Netbook Tips for Using a Netbook Effectively Book VII Chapter 1: Installing and Configuring Windows Server 2008 R2 Planning a Windows Server Installation Checking system requirements Reading the release notes
- 30. Deciding whether to upgrade or install Considering your licensing options Thinking about multiboot Choosing a file system Planning your partitions Deciding your TCP/IP configuration Choosing workgroups or domains Before You Install . . . Backing up Checking the event logs Uncompressing data Disconnecting UPS devices Running Setup Adding Server Roles and Features Chapter 2: Managing Windows Server 2008 Using the Administrator Account Using Remote Desktop Connection Enabling remote access Connecting remotely Using Microsoft Management Console Working with MMC An overview of the MMC consoles Customizing MMC Adding snap-ins Adding taskpads Chapter 3: Dealing with Active Directory What Directories Do Remembering the Good-Ol' Days of NT Domains PDCs and BDCs Trusts NetBIOS names Active Directory to the Rescue Understanding How Active Directory Is Structured Objects Domains Organizational units Trees Forests Creating a Domain Creating an Organizational Unit Chapter 4: Managing Windows User Accounts Understanding Windows User Accounts
- 31. Local accounts versus domain accounts User account properties Creating a New User Setting User Properties Changing the user's contact information Setting account options Specifying logon hours Restricting access to certain computers Setting the user's profile information Resetting User Passwords Disabling and Enabling User Accounts Deleting a User Working with Groups Group types Group scope Default groups Creating a group Adding a member to a group User Profiles Types of user profiles Creating a roaming profile Creating a Logon Script Chapter 5: Managing a File Server Understanding Permissions Understanding Shares Configuring the File Server Role Managing Your File Server Using the Provision a Shared Folder Wizard Sharing a folder without the wizard Granting permissions Chapter 6: Using Group Policy Understanding Group Policy Enabling Group Policy Management on Windows Server 2008 Creating Group Policy Objects Filtering Group Policy Objects Chapter 7: Troubleshooting Working with the Event Viewer Using the Event Viewer Setting event log policies Monitoring Performance Using the Reliability and Performance Monitor Creating performance logs
- 32. Using the Computer Management Console Working with Services Chapter 8: Windows Commands Using a Command Window Opening and closing a command window Editing commands Using the Control menu Special Command Tricks Wildcards Chaining commands Redirection and piping Environment variables Batch files The EventCreate Command Net Commands The Net Accounts command The Net Computer command The Net Config command The Net Continue command The Net File command The Net Group command The Net Help command The Net Helpmsg command The Net Localgroup command The Net Name command The Net Pause command The Net Print command The Net Send command The Net Session command The Net Share command The Net Start command The Net Statistics command The Net Stop command The Net Time command The Net Use command The Net User command The Net View command The RunAs Command Book VIII Chapter 1: Using Internet Information System (IIS) Installing IIS Understanding the Default Web Site
- 33. Creating Web Sites Chapter 2: Managing Exchange Server 2010 Creating a Mailbox Managing Mailboxes Enabling Mailbox Features Creating a Forwarder Setting Mailbox Storage Limits Configuring Outlook for Exchange Viewing Another Mailbox Chapter 3: Using SQL Server 2008 What Is a Database? What Is a Relational Database? What Is SQL? SQL dialects SQL statements Using the select statement Installing SQL Server 2008 Using the SQL Server 2008 Management Studio Creating a New Database Creating Tables Editing Tables Working with Queries Working with Scripts Chapter 4: Using SharePoint What Is SharePoint? Connecting to a SharePoint Site Adding Users Adding and Removing Announcements Creating New Pages Editing the Quick Launch Menu Working with Document Libraries Book IX Chapter 1: Installing a Linux Server Planning a Linux Server Installation Checking system requirements Choosing a distribution Thinking about multiboot Planning your partitions Deciding on your TCP/IP configuration Installing Fedora 7 Using the Setup Agent Chapter 2: Getting Used to Linux
- 34. Linux: It Isn't Windows X Window Virtual consoles Understanding the file system On Again, Off Again Logging on Logging off Shutting down Using GNOME Getting to a Command Shell Managing User Accounts Chapter 3: Basic Linux Network Configuration Using the Network Configuration Program Restarting Your Network Working with Network Configuration Files The Network file The ifcfg files The Hosts file The resolv.conf file The nsswitch.conf file The xinetd.conf file Displaying Your Network Configuration with the ifconfig Command Chapter 4: Running DHCP and DNS Running a DHCP Server Installing DHCP Configuring DHCP Starting DHCP Running a DNS Server Installing BIND Looking at BIND configuration files Restarting BIND Chapter 5: Doing the Samba Dance Understanding Samba Installing Samba Starting and Stopping Samba Using the Samba Server Configuration Tool Configuring server settings Configuring Samba users Creating a share Editing the smb.conf File Using the Samba Client
- 35. Chapter 6: Running Apache Installing Apache Starting and Stopping Apache Confirming that Apache Is Running Using the HTTP Configuration Tool Restricting Access to an Apache Server Configuring Virtual Hosts Configuring the default host Creating a virtual host Setting the Apache User Account Manually Editing Apache's Configuration Files Creating Web Pages Chapter 7: Running Sendmail Understanding E-Mail Installing Sendmail Modifying sendmail.mc Enabling connections Enabling masquerading Setting up aliases Using SpamAssassin Installing SpamAssassin Customizing SpamAssassin Blacklisting and whitelisting e-mail addresses Using the Mail Console Client Using Evolution Chapter 8: Running FTP Installing vsftpd Starting the vsftpd Service Configuring FTP Chapter 9: Linux Commands Command Shell Basics Getting to a shell Editing commands Wildcards Redirection and piping Environment variables Shell scripts Directory and File Handling Commands The pwd command The cd command The mkdir command The rmdir command
- 36. The ls command The cp command The rm command The mv command The touch command The cat command Commands for Working with Packages and Services The service command The rpm command Commands for Administering Users The useradd command The usermod command The userdel command The chage command The passwd command The newusers command The groupadd command The groupdel command The gpasswd command Commands for Managing Ownership and Permissions The chown command The chgrp command The chmod command Networking Commands The hostname command The ifconfig command The netstat command The ping command The route command The traceroute command Appendix A: Directory of Useful Web Sites Certification Hardware Home and Small Business Networking Linux Magazines Microsoft Network Standards Organizations Reference Search TCP/IP and the Internet Wireless Networking
- 37. Smartphones Appendix B: Glossary Networking Basics Chapter 1: Understanding Networks In This Chapter Introducing computer networks Finding out all about clients, servers, and peers Understanding the various types of networks Figuring out the disadvantages of networking The first computer network was invented when ancient mathematicians connected their abacuses (or is it abaci?) together with kite string so they could instantly share their abacus answers with each other. Over the years, computer networks became more and more sophisticated. Now, instead of string, networks use electrical cables, fiber-optic cables, or wireless radio signals to connect computers to each other. The purpose, however, has remained the same: sharing information and getting work done faster. This chapter describes the basics of what computer networking is and how it works. What Is a Network? A network is nothing more than two or more computers connected to each other so that they can exchange information, such as e-mail messages or documents, or share resources, such as disk storage or printers. In most cases, this connection is made via electrical cables that carry the information in the form of electrical signals. But in some cases, other types of connections are used. For example, fiber-optic cables let computers communicate at extremely high speeds by using impulses of light. Wireless networks let computers communicate by using radio signals, so the computers aren't restricted by physical cables. In addition to the hardware that comprises the network, a network also requires special software to enable communications. In the early days of networking, you had to add this software to each computer on the network. Nowadays, network support is built in to all major operating systems, including all current versions of Windows, Macintosh operating systems, and Linux. Network building blocks
- 38. All networks, large or small, require specialized network hardware to make them work. For small networks, the hardware may consist of nothing more than a collection of computers that are equipped with network ports, a cable for each computer, and a network switch that all the computers plug in to via the cable. Larger networks probably have additional components, such as routers or repeaters. Small or large, all networks are built from the following basic building blocks: ♦ Client computers: The computers that end users use to access the resources of the network. Client computers are typically computers located on users' desks. They usually run a desktop version of Windows such as Windows 7, Vista, or XP. In addition, the client computers usually run some type of application software such as Microsoft Office. Client computers are sometimes referred to as workstations. ♦ Server computers: Computers that provide shared resources, such as disk storage and printers, as well as network services, such as e-mail and Internet access. Server computers typically run a specialized network operating system such as Windows Server 2008 or 2003, NetWare, or Linux, along with special software to provide network services. For example, a server may run Microsoft Exchange to provide e- mail services for the network, or it may run Apache Web Server so that the computer can serve Web pages. ♦ Network interface: An interface — sometimes called a network port — that's installed in a computer to enable the computer to communicate over a network. Almost all network interfaces implement a networking standard called Ethernet. A network interface is sometimes called a NIC, which stands for network interface card,because in the early days of networking you actually had to install a separate circuit card in the computer to provide a network interface. Nowadays, nearly all computers come with network interfaces built in as an integral part of the computer's motherboard. Although separate network cards are rarely required these days, the term NIC is still frequently used to refer to the network interface. It's still common to install separate network interface cards to provide more than one network interface on a single computer, or to replace a built-in network interface that has malfunctioned without having to replace the entire motherboard. ♦ Cable: Computers in a network are usually physically connected to each other using cable. Although several types of cable have been popular over the years, most networks today use a type of cable called twisted-pair, also known by its official designation10BaseT. Twisted-pair cable is also sometimes referred to as Cat-5 or Cat-6 cable. These terms refer to the standards that determine the maximum speed with which the cable can carry data, Cat-6 being rated for more speed than Cat-5. Twisted-pair cable can also be referred to simply as copper, to distinguish it from fiber-optic cable which is used for the highest-speed network connections. Fiber-optic cable uses strands of glass to transmit light signals at very high speeds. In many cases, the cables run through the walls and converge on a central room called awiring closet. But for smaller networks, the cables are often just strung along the floor, hidden behind desks and other furniture whenever possible. ♦ Switches: Network cable usually doesn't connect computers directly to each other. Instead, each computer is connected by cable to a device known as a switch. The switch, in turn, connects to the rest of the network. Each switch contains a certain number of ports,typically 8 or 16. Thus, you can use an eight- port switch to connect up to eight computers. Switches can be connected to each other to build larger networks. For more information about switches, see the "Network Topology" section later in this chapter. (Older networks may use a more primitive type of device called a hub instead of a switch. A hub provides the same function as a switch, but it isn't as efficient. The term hub is sometimes used to meanswitch, even though hubs and switches are not technically the same thing.) ♦ Wireless networks: In many networks, cables and switches are making way for wireless network connections, which enable computers to communicate via radio signals. In a wireless network, radio transmitters and receivers take the place of cables. The main advantage of wireless networking is its flexibility. With a wireless network, you don't have to run cables through walls or ceilings, and your client computers can be located anywhere within range of the network broadcast. The main disadvantage of wireless networking is that it's inherently less secure than a cabled network.
- 39. ♦ Network software: Although network hardware is essential, what really makes a network work is software. A whole bunch of software has to be set up just right in order to get a network working. Server computers typically use a special network operating system(also known as a NOS) in order to function efficiently, and client computers need to have their network settings configured properly in order to access the network. One of the most important networking choices to make is which network operating system you'll use on the network's servers. That's because much of the task of building a new network and managing an existing one is setting up and maintaining the network operating system on the servers. Why bother? If the truth be told, computer networks are a pain to set up. So, why bother? Because the benefits of having a network make the difficulty of setting one up worthwhile. You don't have to be a Ph.D. to understand the benefits of networking. In fact, you learned everything you need to know about the benefits of networking in kindergarten. Networks are all about sharing. Specifically, networks are about sharing three things: information, resources, and applications. ♦ Sharing information: Networks allow users to share information in several different ways. The most common way of sharing information is to share individual files. For example, two or more people can work together on a single spreadsheet file or word-processing document. In most networks, a large hard drive on a central server computer is set up as a common storage area where users can store files to be shared with other users. In addition to sharing files, networks allow users to communicate with each other in various ways. For example, messaging applications let network users exchange messages with each other using an e-mail application such as Microsoft Outlook. Users can also hold online meetings over the network. In fact, with inexpensive video cameras and the right software, users can hold videoconferences over the network. ♦ Sharing resources: Certain computer resources, such as printers or hard drives, can be set up so that network users can share them. Sharing these resources can result in significant cost savings. For example, it's cheaper to buy a single high-speed printer with advanced features such as collating, stapling, and duplex printing that can be shared by an entire workgroup than it is to buy separate printers for each user in the group. Hard drives can also be shared resources. In fact, providing users with access to a shared hard drive is the most common method of sharing files on a network. A computer whose main purpose in life is to host shared hard drives is called a file server. In actual practice, entire hard drives aren't usually shared. Instead, individual folders on a networked hard drive are shared. This way, the network administrator can allow different network users to have access to different shared folders. For example, a company may set up shared folders for its sales department and accounting department. Then, sales personnel can access the sales department's folder, and accounting personnel can access the accounting department's folder. You can share other resources on a network. For example, a network can be used to share an Internet connection. In the early days of the Internet, it was common for each user who required access to the Internet to have his or her own modem connection. Nowadays, it's more common for the network to provide a shared, high-speed Internet connection that everyone on the network can access. ♦ Sharing applications: One of the most common reasons for networking in many businesses is so that several users can work together on a single business application. For example, an accounting department may have accounting software that can be used from several computers at the same time. Or a sales- processing department may have an order-entry application that runs on several computers to handle a large volume of orders. Of Clients and Servers The network computer that contains the hard drives, printers, and other resources that are shared with other network computers is called a server. This term comes up repeatedly, so you have to remember it. Write it on the back of your left hand. Any computer that's not a server is called a client. You have to remember this term, too. Write it on the back of your right hand. Only two kinds of computers are on a network: servers and clients. Look at your left hand and then look at your right hand. Don't wash your hands until you have these terms memorized.
- 40. The distinction between servers and clients in a network would be somewhat fun to study in a sociology class because it's similar to the distinction between the haves and the have-nots in society: ♦ Usually, the most powerful and expensive computers in a network are the servers. This fact makes sense because every user on the network shares the server's resources. ♦ The cheaper and less powerful computers in a network are the clients. Clients are the computers used by individual users for everyday work. Because clients' resources don't have to be shared, they don't have to be as fancy. ♦ Most networks have more clients than servers. For example, a network with ten clients can probably get by with one server. ♦ In some networks, a clear line of segregation exists between servers and clients. In other words, a computer is either a server or a client, and not both. A server can't become a client, nor can a client become a server. ♦ Other networks are more progressive, allowing any computer in the network to be a server and allowing any computer to be both server and client at the same time. The network illustrated in Figure 1-1, later in this chapter, is this type of network. Dedicated Servers and Peers In some networks, a server computer is a server computer and nothing else. This server computer is dedicated solely to the task of providing shared resources, such as hard drives and printers, to be accessed by the network client computers. Such a server is referred to as a dedicated server because it can perform no other tasks besides network services. A network that relies on dedicated servers is sometimes called a client/server network. Other networks take an alternative approach, enabling any computer on the network to function as both a client and a server. Thus, any computer can share its printers and hard drives with other computers on the network. And while a computer is working as a server, you can still use that same computer for other functions such as word processing. This type of network is called a peer-to-peer network because all the computers are thought of as peers, or equals. While you're walking the dog tomorrow morning, ponder these points concerning the difference between dedicated server networks and peer-to-peer networks: ♦ Peer-to-peer networking has been built in to all versions of Windows since Windows 95. Thus, you don't have to buy any additional software to turn your computer into a server. All you have to do is enable the Windows server features. ♦ The network server features that are built in to desktop versions of Windows (including Windows 7, Vista, and XP) aren't very efficient because these versions of Windows were not designed primarily to be network servers. If you're going to dedicate a computer to the task of being a full-time server, you should use a full-fledged network operating system, such as Windows Server 2008, instead. Networks Big and Small Networks come in all sizes and shapes. In fact, it's common to categorize networks based on the geographical size they cover, as described in the following list: ♦ Local area networks: A local area network, or LAN, is a network in which computers are relatively close together, such as within the same office or building. Note that the term LAN doesn't imply that the network is small. A LAN can, in fact, contain hundreds or even thousands of computers. What makes a network a LAN is that all those computers are located within close proximity to each other. Usually a LAN is contained within a single building, but a LAN can extend to several buildings on a campus — provided the buildings are close to each other (typically within 300 feet of each other, though greater distances are possible with special equipment). ♦ Wide area networks: A wide area network, or WAN, is a network that spans a large geographic territory, such as an entire city or region, or even an entire country. WANs are typically used to connect two or more LANs that are relatively far apart. For example, a WAN may connect an office in San Francisco with an office in New York. Again, it's the geographic distance, not the number of computers involved, that makes a network a WAN. If the office in San Francisco and the office in New York both have only one computer, the WAN will have a total of two computers but will span more than 3,000 miles. ♦ Metropolitan area networks: A metropolitan area network, or MAN, is a network that's smaller than a typical WAN but larger than a LAN. Typically, a MAN connects two or more LANs that are within
- 41. the same city but are far enough apart that the networks can't be connected using a simple cable or wireless connection. Network Topology The term network topology refers to the shape of how the computers and other network components are connected to each other. There are several different types of network topologies, each with advantages and disadvantages. In the following discussion of network topologies, I use two important terms: ♦ Node: A node is a device that's connected to the network. For your purposes here, a node is the same as a computer. Network topology deals with how the nodes of a network are connected to each other. ♦ Packet: A packet is a message that's sent over the network from one node to another node. The packet includes the address of the node that sent the packet, the address of the node the packet is being sent to, and data. Bus topology The first type of network topology is called a bus, in which nodes are strung together in a line, as shown in Figure 1-1. The key to understanding how a bus topology works is to think of the entire network as a single cable, with each node "tapping" into the cable so it can listen in on the packets being sent over that cable. If you're old enough to remember party lines, you get the idea. Figure 1-1: Bus topology. In a bus topology, every node on the network can see every packet that's sent on the cable. Each node looks at each packet to determine whether the packet is intended for it. If so, the node claims the packet. If not, the node ignores the packet. This way, each computer can respond to data sent to it and ignore data sent to other computers on the network. If the cable in a bus network breaks, the entire network is effectively disabled. Obviously the nodes on opposite sides of the break can't continue to communicate with each other because data can't span the gap created by the break. But even those nodes that are on the same side of the break will be unable to communicate with each other, because the open end of the cable left by the break disrupts the proper transmission of electrical signals. In the early days of Ethernet networking, bus topology was commonplace. Although bus topology has given way to star topology (see the next section) for most networks today, many networks today still have elements that rely on bus topology. Star topology In a star topology, each network node is connected to a central device called a hub or aswitch, as shown in Figure 1-2. Star topologies are commonly used with LANs. If a cable in a star network breaks, only the node connected to that cable is isolated from the network. The other nodes can continue to operate without interruption — unless, of course, the node that's isolated because of the break happens to be the file server. You should be aware of the somewhat technical distinction between a hub and a switch. Simply put, a hub doesn't know anything about the computers that are connected to each of its ports. So when a computer connected to the hub sends a packet to a computer that's connected to another port, the hub
- 42. sends a duplicate copy of the packet to all its ports. In contrast, a switch knows which computer is connected to each of its ports. As a result, when a switch receives a packet intended for a particular computer, it sends the packet only to the port that the recipient is connected to. Figure 1-2: Star topology. Strictly speaking, only networks that use switches have a true star topology. If the network uses a hub, the network topology has the physical appearance of a star, but is actually a bus. That's because when a hub is used, each computer on the network sees all the packets sent over the network, just like in a bus topology. In a true star topology, as when a switch is used, each computer sees only those packets that were sent specifically to it, as well as packets that were specifically sent to all computers on the network (those types of packets are called broadcast packets). Expanding stars Physicists say that the universe is expanding, and network administrators know they're right. A simple bus or star topology is suitable only for small networks, with a dozen or so computers. But small networks inevitably become large networks as more computers are added. For larger networks, it's common to create more complicated topologies that combine stars and buses. For example, a bus can be used to connect several stars. In this case, two or more hubs or switches are connected to each other using a bus. Each of these hubs or switches is then the center of a star that connects two or more computers to the network. This type of arrangement is commonly used in buildings that have two or more distinct workgroups. The bus that connects the switches is sometimes called a backbone. Another way to expand a star topology is to use a technique called daisy-chaining. When you use daisy- chaining, a switch is connected to another switch as if it were one of the nodes on the star. Then, this second switch serves as the center of a second star. Ring topology
- 43. A third type of network topology is called a ring, shown in Figure 1-3. In a ring topology, packets are sent around the circle from computer to computer. Each computer looks at each packet to decide whether the packet was intended for it. If not, the packet is passed on to the next computer in the ring. Figure 1-3: Ring topology. Years ago, ring topologies were common in LANs, as two popular networking technologies used rings: ARCNET and Token Ring. ARCNET is still used for certain applications such as factory automation, but is rarely used in business networks. Token Ring is still a popular network technology for IBM midrange computers. Although plenty of Token Ring networks are still in existence, not many new networks use Token Ring any more. Ring topology was also used by FDDI, one of the first types of fiber-optic network connections. FDDI has given way to more efficient fiber-optic techniques, however. So ring networks have all but vanished from business networks. Mesh topology A fourth type of network topology, known as mesh, has multiple connections between each of the nodes on the network, as shown in Figure 1-4. The advantage of a mesh topology is that if one cable breaks, the network can use an alternative route to deliver its packets. Figure 1-4: Mesh topology.
- 44. Mesh networks aren't very practical in a LAN setting. For example, to network eight computers in a mesh topology, each computer would have to have seven network interface cards, and 28 cables would be required to connect each computer to the seven other computers in the network. Obviously, this scheme isn't very scalable. However, mesh networks are common for metropolitan or wide area networks. These networks use devices called routers to route packets from network to network. For reliability and performance reasons, routers are usually arranged in a way that provides multiple paths between any two nodes on the network in a meshlike arrangement. Chapter 2: Understanding Network Protocols and Standards In This Chapter Deciphering the layers of the OSI reference model Understanding an Ethernet Getting the inside scoop on TCP/IP and IPX/SPX Finding out about other important protocols Protocols and standards are what make networks work together. Protocols make it possible for the various components of a network to communicate with each other. Standards also make it possible for network components manufactured by different companies to work together. This chapter introduces you to the protocols and standards that you're most likely to encounter when building and maintaining a network. Understanding Protocols A protocol is a set of rules that enables effective communications to occur. You encounter protocols every day. For example, when you pay for groceries with a debit card, the clerk first tells you how much the groceries cost. You then swipe your debit card in the card reader, punch in your security code, indicate whether you want cash back, enter the amount of the cash back if you so indicated, then verify the total amount. You then cross your fingers behind your back and say a quiet prayer while the machine authorizes the purchase. Assuming the amount is authorized, the machine prints out your receipt. Here's another example of an everyday protocol: making a phone call. You probably take most of the details of the phone-calling protocol for granted, but it's pretty complicated if you think about it: ♦ When you pick up a phone, you must listen for a dial tone before dialing the number (unless you're using a cell phone). If you don't hear a dial tone, you know that either (1) someone else in your family is talking on the phone or (2) something is wrong with your phone. ♦ When you hear the dial tone, you initiate the call by dialing the number of the party you want to reach. If the person you want to call is in the same area code as you, most of the time you simply dial that person's seven-digit phone number. If the person is in a different area code, you dial a one, the three-digit area code, and the person's seven-digit phone number. ♦ If you hear a series of long ringing tones, you wait until the other person answers the phone. If the phone rings a certain number of times with no answer, you hang up and try again later. If you hear a voice say, "Hello," you begin a conversation with the other party. If the person on the other end of the phone has never heard of you, you say, "Sorry, wrong number," hang up, and try again.
- 45. ♦ If you hear a voice that rambles on about how they're not home but they want to return your call, you wait for a beep and leave a message. ♦ If you hear a series of short tones, you know the other person is talking to someone else on the phone. So you hang up and try again later. ♦ If you hear a sequence of three tones that increase in pitch, followed by a recorded voice that says "We're sorry . . ." you know that the number you dialed is invalid. Either you dialed the number incorrectly, or the number has been disconnected. I can go on and on, but I think you probably get the point. Exchanges such as using debit cards or making phone calls follow the same rules every time they happen. Computer networks depend upon many different types of protocols in order to work. These protocols are very rigidly defined, and for good reason. Network cards must know how to talk to other network cards in order to exchange information, operating systems must know how to talk to network cards in order to send and receive data on the network, and application programs must know how to talk to operating systems in order to know how to retrieve a file from a network server. Protocols come in many different types. At the lowest level, protocols define exactly what type of electrical signal represents a one and what type of signal represents a zero. At the highest level, protocols allow a computer user in the United States to send an e-mail to another computer user in New Zealand. And in between are many other levels of protocols. You find out more about these levels of protocols (which are often called layers) in the section, "The Seven Layers of the OSI Reference Model," later in this chapter. Various protocols tend to be used together in matched sets called protocol suites. The two most popular protocol suites for networking are TCP/IP andEthernet. TCP/IP was originally developed for Unix networks and is the protocol of the Internet and most local-area networks. Ethernet is a low-level protocol that spells out the electrical characteristics of the network hardware used by most local-area networks. A third important protocol is IPX/SPX, which is an alternative to TCP/IP that was originally developed for NetWare networks. In the early days of networking, IPX/SPX was widely used in local area networks, but TCP/IP is now the preferred protocol. Understanding Standards A standard is an agreed-upon definition of a protocol. In the early days of computer networking, each computer manufacturer developed its own networking protocols. As a result, you weren't able to easily mix equipment from different manufacturers on a single network. Then along came standards to save the day. Standards are industry-wide protocol definitions that are not tied to a particular manufacturer. With standard protocols, you can mix and match equipment from different vendors. As long as the equipment implements the standard protocols, it should be able to coexist on the same network. Many organizations are involved in setting standards for networking. The five most important organizations are ♦ American National Standards Institute (ANSI): The official standards organization in the United States. ANSI is pronounced AN-see. ♦ Institute of Electrical and Electronics Engineers (IEEE): An international organization that publishes several key networking standards — in particular, the official standard for the Ethernet networking system (known officially as IEEE 802.3). IEEE is pronounced eye-triple-E. ♦ International Organization for Standardization (ISO): A federation of more than 100 standards organizations from throughout the world. If I had studied French in high school, I'd probably understand why the acronym for International Organization for Standardization is ISO, and not IOS. ♦ Internet Engineering Task Force (IETF): The organization responsible for the protocols that drive the Internet. ♦ World Wide Web Consortium (W3C): An international organization that handles the development of standards for the World Wide Web. Table 2-1 lists the Web sites for each of these standards organizations.
- 46. The Seven Layers of the OSI Reference Model OSI sounds like the name of a top-secret government agency you hear about only in Tom Clancy novels. What it really stands for in the networking world is Open Systems Interconnection, as in the Open Systems Interconnection Reference Model, affectionately known as the OSI model. The OSI model breaks the various aspects of a computer network into seven distinct layers. These layers are kind of like the layers of an onion: Each successive layer envelops the layer beneath it, hiding its details from the levels above. The OSI model is also like an onion in that if you start to peel it apart to have a look inside, you're bound to shed a few tears. The OSI model is not a networking standard in the same sense that Ethernet and TCP/IP are networking standards. Rather, the OSI model is a framework into which the various networking standards can fit. The OSI model specifies what aspects of a network's operation can be addressed by various network standards. So, in a sense, the OSI model is sort of a standard of standards. Table 2-2 summarizes the seven layers of the OSI model.
- 47. The first three layers are sometimes called the lower layers. They deal with the mechanics of how information is sent from one computer to another over a network. Layers 4 through 7 are sometimes called the upper layers. They deal with how application software can relate to the network through application programming interfaces. The following sections describe each of these layers in greater detail. The seven layers of the OSI model are a somewhat idealized view of how networking protocols should work. In the real world, actual networking protocols don't follow the OSI model to the letter. The real world is always messier than we'd like. Still, the OSI model provides a convenient — if not completely accurate — conceptual picture of how networking works. The Physical Layer The bottom layer of the OSI model is the Physical layer. It addresses the physical characteristics of the network, such as the types of cables used to connect devices, the types of connectors used, how long the cables can be, and so on. For example, the Ethernet standard for 10BaseT cable specifies the electrical characteristics of the twisted-pair cables, the size and shape of the connectors, the maximum length of the cables, and so on. The star, bus, ring, and mesh network topologies described in Book I, Chapter 1 apply to the Physical layer. Another aspect of the Physical layer is the electrical characteristics of the signals used to transmit data over the cables from one network node to another. The Physical layer doesn't define any meaning to those signals other than the basic binary values of zero and one. The higher levels of the OSI model must assign meanings to the bits that are transmitted at the Physical layer. One type of Physical layer device commonly used in networks is a repeater. A repeater is used to regenerate the signal whenever you need to exceed the cable length allowed by the Physical layer standard. 10BaseT hubs are also Physical layer devices. Technically, they're known as multiport repeaters because the purpose of a hub is to regenerate every packet received on any port on all of the hub's other ports. Repeaters and hubs don't examine the contents of the packets that they regenerate. If they did, they would be working at the Data Link layer, and not at the Physical layer. The network adapter (also called a network interface card or NIC) that's installed in each computer on the network is a Physical layer device. You can display information about the network adapter (or adapters) installed in a Windows computer by displaying the adapter's Properties dialog box, as shown in Figure 2-1. To access this dialog box in Windows 7 or Vista, open the Control Panel, choose Network and Internet, choose View Network Status and Tasks, and choose Change Adapter Settings. Then, right-click the Local Area Connection icon and choose Properties from the menu that appears. Figure 2-1: The Properties dialog box for a network adapter.
- 48. The Data Link Layer The Data Link layer is the lowest layer at which meaning is assigned to the bits that are transmitted over the network. Data link protocols address things such as the size of each packet of data to be sent, a means
- 49. of addressing each packet so that it's delivered to the intended recipient, and a way to ensure that two or more nodes don't try to transmit data on the network at the same time. The Data Link layer also provides basic error detection and correction to ensure that the data sent is the same as the data received. If an uncorrectable error occurs, the data link standard must specify how the node is to be informed of the error so that it can retransmit the data. At the Data Link layer, each device on the network has an address known as the Media Access Control address, or MAC address. This address is actually hard-wired into every network device by the manufacturer. MAC addresses are unique; no two network devices made by any manufacturer anywhere in the world can have the same MAC address. You can see the MAC address for a computer's network adapter by opening a command window and running the ipconfig /all command, as shown in Figure 2-2. In this example, the MAC address of the network card is A4-BA-DB-01-99-E8. (The ipconfigcommand refers to the MAC address as the physical address.) Figure 2-2: Using the ipconfig /all command to display the MAC address of a network adapter. One of the most import functions of the Data Link layer is to provide a way for packets to be sent safely over the physical media without interference from other nodes attempting to send packets at the same time. The two most popular ways to do this are CSMA/CD and token passing. Ethernet networks use CSMA/CD, and Token Ring networks use token passing. Two types of Data Link layer devices are commonly used on networks: bridges and switches. A bridge is an intelligent repeater that is aware of the MAC addresses of the nodes on either side of the bridge and can forward packets accordingly. A switch is an intelligent hub that examines the MAC address of arriving packets in order to determine which port to forward the packet to.
- 50. An important function of the Data Link layer is to make sure that two computers don't try to send packets over the network at the same time. If they do, the signals will collide with each other, and the transmission will be garbled. Ethernet accomplishes this feat by using a technique called CSMA/CD, which stands for carrier sense multiple access with collision detection. This phrase is a mouthful, but if you take it apart piece by piece, you'll get an idea of how it works. Carrier sense means that whenever a device wants to send a packet over the network media, it first listens to the network media to see whether anyone else is already sending a packet. If it doesn't hear any other signals on the media, the computer assumes that the network is free, so it sends the packet. Multiple access means that nothing prevents two or more devices from trying to send a message at the same time. Sure, each device listens before sending. However, suppose that two devices listen, hear nothing, and then proceed to send their packets at the same time? Picture what happens when you and someone else arrive at a four-way stop sign at the same time. You wave the other driver on, he or she waves you on, you wave, he or she waves, you both wave, and then you both go at the same time. Collision detection means that after a device sends a packet, it listens carefully to see whether the packet crashes into another packet. This is kind of like listening for the screeching of brakes at the four-way stop. If the device hears the screeching of brakes, it waits a random period of time and then tries to send the packet again. Because the delay is random, two packets that collide are sent again after different delay periods, so a second collision is unlikely. CSMA/CD works pretty well for smaller networks. After a network hits about 30 computers, however, packets start to collide like crazy, and the network slows to a crawl. When that happens, the network should be divided into two or more separate sections that are sometimes called collision domains. The Network Layer The Network layer handles the task of routing network messages from one computer to another. The two most popular layer 3 protocols are IP (which is usually paired with TCP) and IPX (normally paired with SPX for use with Novell and Windows networks). Network layer protocols provide two important functions: logical addressing and routing. The following sections describe these functions. Logical addressing As you know, every network device has a physical address called a MAC address, which is assigned to the device at the factory. When you buy a network interface card to install into a computer, the MAC address of that card is fixed and can't be changed. But what if you want to use some other addressing scheme to refer to the computers and other devices on your network? This is where the concept of logical addressing comes in; a logical address lets you access a network device by using an address that you assign. Logical addresses are created and used by Network layer protocols such as IP or IPX. The Network layer protocol translates logical addresses to MAC addresses. For example, if you use IP as the Network layer protocol, devices on the network are assigned IP addresses such as 207.120.67.30. Because the IP protocol must use a Data Link layer protocol to actually send packets to devices, IP must know how to translate the IP address of a device to the device's MAC address. You can use the ipconfig command shown earlier in Figure 2-2 to see the IP address of your computer. The IP address shown in the figure is 192.168.1.100. Another way to display this information is to use the System Information command, found on the Start menu under Start⇒All Programs⇒Accessories⇒System Tools⇒System Information. The IP address is highlighted in Figure 2-3. Notice that the System Information program displays a lot of other useful information about the network besides the IP address. For example, you can also see the MAC address, what protocols are being used, and other information. Figure 2-3: Displaying network information using the System Information program.
- 51. Although the exact format of logical addresses varies depending on the protocol being used, most protocols divide the logical address into two parts: a network address and a device address. The network address identifies which network the device resides on, and the device address then identifies the device on that network. For example, in a typical IP address, such as 192.168.1.102, the network address is 192.168.1, and the device address (called a host address in IP) is 102. Similarly, IPX addresses consist of two parts: a network address and a node address. In an IPX address, the node address is the same as the MAC address. As a result, IPX doesn't have to translate between layer 3 and layer 2 addresses. Routing Routing comes into play when a computer on one network needs to send a packet to a computer on another network. In this case, a device called a router is used to forward the packet to the destination network. In some cases, a packet may actually have to travel through several intermediate networks in order to reach its final destination network. You can find out more about routers in Book I, Chapter 3. An important feature of routers is that you can use them to connect networks that use different layer 2 protocols. For example, a router can be used to send a packet from an Ethernet to a Token Ring network. As long as both networks support the same layer 3 protocol, it doesn't matter whether their layer 1 and layer 2 protocols are different. A protocol is considered routable if it uses addresses that include a network part and a host part. Any protocol that uses physical addresses isn't routable because physical addresses don't indicate to which network a device belongs. The Transport Layer
- 52. The Transport layer is the layer where you'll find two of the most well-known networking protocols: TCP (normally paired with IP) and SPX (normally paired with IPX). As its name implies, the Transport layer is concerned with the transportation of information from one computer to another. The main purpose of the Transport layer is to ensure that packets are transported reliably and without errors. The Transport layer does this task by establishing connections between network devices, acknowledging the receipt of packets, and resending packets that aren't received or are corrupted when they arrive. In many cases, the Transport layer protocol divides large messages into smaller packets that can be sent over the network efficiently. The Transport layer protocol reassembles the message on the receiving end, making sure that all the packets that comprise a single transmission are received so that no data is lost. For some applications, speed and efficiency are more important than reliability. In such cases, a connectionless protocol can be used. A connectionless protocol doesn't go to the trouble of establishing a connection before sending a packet. Instead, it simply sends the packet. TCP is a connection-oriented Transport layer protocol. The connectionless protocol that works alongside TCP is called UDP. In Windows XP or Vista, you can view information about the status of TCP and UDP connections by running the Netstat command from a command window, as Figure 2-4 shows. In the figure, you can see that several TCP connections are established. Figure 2-4: Using the Netstat command. In fact, you can use the command Netstat /N to see the numeric network addresses instead of the names. With the /N switch, the output in Figure 2-4 would look like this: Active Connections Proto Local Address Foreign Address State TCP 127.0.0.1:2869 127.0.0.1:54170 ESTABLISHED TCP 127.0.0.1:5357 127.0.0.1:54172 TIME_WAIT TCP 127.0.0.1:27015 127.0.0.1:49301 ESTABLISHED TCP 127.0.0.1:49301 127.0.0.1:27015 ESTABLISHED TCP 127.0.0.1:54170 127.0.0.1:2869 ESTABLISHED TCP 192.168.1.100:49300 192.168.1.101:445 ESTABLISHED
- 53. TCP is a connection-oriented Transport layer protocol. UDP is a connectionless Transport layer protocol. The Session Layer The Session layer establishes conversations known as sessions between networked devices. A session is an exchange of connection-oriented transmissions between two network devices. Each of these transmissions is handled by the Transport layer protocol. The session itself is managed by the Session layer protocol. A single session can include many exchanges of data between the two computers involved in the session. After a session between two computers has been established, it is maintained until the computers agree to terminate the session. The Session layer allows three types of transmission modes: ♦ Simplex: In this mode, data flows in only one direction. ♦ Half-duplex: In this mode, data flows in both directions, but only in one direction at a time. ♦ Full-duplex: In this mode, data flows in both directions at the same time. In actual practice, the distinctions in the Session, Presentation, and Application layers are often blurred, and some commonly used protocols actually span all three layers. For example, SMB — the protocol that is the basis of file sharing in Windows networks — functions at all three layers. The Presentation Layer The Presentation layer is responsible for how data is represented to applications. Most computers — including Windows, Unix, and Macintosh computers — use the American Standard Code for Information Interchange (ASCII) to represent data. However, some computers (such as IBM mainframe computers) use a different code, known as Extended Binary Coded Decimal Interchange Code (EBCDIC). ASCII and EBCDIC aren't compatible with each other. To exchange information between a mainframe computer and a Windows computer, the Presentation layer must convert the data from ASCII to EBCDIC and vice versa. Besides simply converting data from one code to another, the Presentation layer can also apply sophisticated compression techniques so that fewer bytes of data are required to represent the information when it's sent over the network. At the other end of the transmission, the Presentation layer then uncompresses the data. The Presentation layer can also scramble the data before it is transmitted and unscramble it at the other end by using a sophisticated encryption technique that even Sherlock Holmes would have trouble breaking. The Application Layer The highest layer of the OSI model, the Application layer, deals with the techniques that application programs use to communicate with the network. The name of this layer is a little confusing. Application programs such as Microsoft Office or QuickBooks aren't a part of the Application layer. Rather, the Application layer represents the programming interfaces that application programs such as Microsoft Office or QuickBooks use to request network services. Some of the better-known Application layer protocols are ♦ DNS (Domain Name System) for resolving Internet domain names. ♦ FTP (File Transfer Protocol) for file transfers. ♦ SMTP (Simple Mail Transfer Protocol) for e-mail. ♦ SMB (Server Message Block) for file sharing in Windows networks. ♦ NFS (Network File System) for file sharing in Unix networks. ♦ Telnet for terminal emulation. Following a Packet through the Layers Figure 2-5 shows how a packet of information flows through the seven layers as it travels from one computer to another on the network. The data begins its journey when an end-user application sends data to another network computer. The data enters the network through an Application layer interface,
- 54. such as SMB. The data then works its way down through the protocol stack. Along the way, the protocol at each layer manipulates the data by adding header information, converting the data into different formats, combining packets to form larger packets, and so on. When the data reaches the Physical layer protocol, it's actually placed on the network media (in other words, the cable) and sent to the receiving computer. When the receiving computer receives the data, the data works its way up through the protocol stack. Then, the protocol at each layer reverses the processing that was done by the corresponding layer on the sending computer. Headers are removed, data is converted back to its original format, packets that were split into smaller packets are recombined into larger messages, and so on. When the packet reaches the Application layer protocol, it's delivered to an application that can process the data. Figure 2-5: How data travels through the seven layers.
- 55. The Ethernet Protocol As you know, the first two layers of the OSI model deal with the physical structure of the network and the means by which network devices can send information from one device on a network to another. By far, the most popular set of protocols for the Physical and Data Link layers is Ethernet. Ethernet has been around in various forms since the early 1970s. (For a brief history of Ethernet, see the sidebar, "Ethernet folklore and mythology," later in this chapter.) The current incarnation of Ethernet is defined by the IEEE standard known as 802.3. Various flavors of Ethernet operate at different speeds and use different types of media. However, all the versions of Ethernet are compatible with each other, so you can mix and match them on the same network by using devices such as bridges, hubs, and switches to link network segments that use different types of media. The actual transmission speed of Ethernet is measured in millions of bits per second, or Mbps. Ethernet comes in three different speed versions: 10 Mbps, known as Standard Ethernet; 100 Mbps, known as Fast Ethernet; and 1,000 Mbps, known as Gigabit Ethernet. Keep in mind, however, that network transmission speed refers to the maximum speed that can be achieved over the network under ideal conditions. In reality, the actual throughput of an Ethernet network rarely reaches this maximum speed. Ethernet operates at the first two layers of the OSI model — the Physical and the Data Link layers. However, Ethernet divides the Data Link layer into two separate layers known as theLogical Link Control (LLC) layer and the Medium Access Control (MAC) layer. Figure 2-6 shows how the various elements of Ethernet match up to the OSI model. Figure 2-6: Ethernet and the OSI model. The following sections describe Standard Ethernet, Fast Ethernet, and Gigabit Ethernet in more detail. Standard Ethernet Standard Ethernet is the original Ethernet. It runs at 10 Mbps, which was considered fast in the 1970s but is pretty slow by today's standards. Although there is still plenty of existing Standard Ethernet in use, it is considered obsolete and should be replaced by Gigabit Ethernet as soon as possible. Standard Ethernet comes in four incarnations, depending on the type of cable used to string the network together: ♦ 10Base5: The original Ethernet cable was thick (about as thick as your thumb), heavy, and difficult to work with. It's seen today only in museums. ♦ 10Base2: This thinner type of coaxial cable (it resembles television cable) became popular in the 1980s and lingered into the early 1990s. Plenty of 10Base2 cable is still in use, but it's rarely installed in new networks. 10Base2 (like 10Base5) uses a bus topology, so wiring a 10Base2 network involves running cable from one computer to the next until all the computers are connected in a segment.
- 56. ♦ 10BaseT: Unshielded twisted-pair cable (also known as UTP) became popular in the 1990s because it's easier to install, lighter, and more reliable, and it offers more flexibility in how networks are designed. 10BaseT networks use a star topology with hubs at the center of each star. Although the maximum length of 10BaseT cable is only 100 meters, hubs can be chained together to extend networks well beyond the 100-meter limit. 10BaseT cable has four pairs of wires that are twisted together throughout the entire span of the cable. However, 10BaseT uses only two of these wire pairs, so the unused pairs are spares. ♦ 10BaseFL: Fiber-optic cables were originally supported at 10 Mbps by the 10BaseFL standard. However, because faster fiber-optic versions of Ethernet now exist, 10BaseFL is rarely used. Fast Ethernet Fast Ethernet refers to Ethernet that runs at 100 Mbps, which is ten times the speed of Standard Ethernet. The following are the three varieties of Fast Ethernet: ♦ 100BaseT4: The 100BaseT4 protocol allows transmission speeds of 100 Mbps over the same UTP cable as 10BaseT networks. To do this, it uses all four pairs of wire in the cable. 100BaseT4 simplifies the task of upgrading an existing 10BaseT network to 100 Mbps. ♦ 100BaseTX: The most commonly used standard for office networks today is 100BaseTX, which transmits at 100 Mbps over just two pairs of a higher grade of UTP cable than the cable used by 10BaseT. The higher-grade cable is referred to as Category 5.Most new networks are wired with Category 5 or better cable. ♦ 100BaseFX: The fiber-optic version of Ethernet running at 100 Mbps is called 100BaseFX. Because fiber-optic cable is expensive and tricky to install, it isn't used much for individual computers in a network. However, it's commonly used as a networkbackbone. For example, a fiber backbone is often used to connect individual workgroup hubs to routers and servers. Ethernet folklore and mythology If you're a history buff, you may be interested in the story of how Ethernet came to be so popular. Here's how it happened: The original idea for the Ethernet was hatched in the mind of a graduate computer science student at Harvard University named Robert Metcalfe. Looking for a thesis idea in 1970, he refined a networking technique that was used in Hawaii, called the AlohaNet (it was actually a wireless network), and developed a technique that would enable a network to efficiently use as much as 90 percent of its capacity. By 1973, he had his first Ethernet network up and running at the famous Xerox Palo Alto Research Center (PARC). Bob dubbed his network "Ethernet" in honor of the thick network cable, which he called "the ether." (Xerox PARC was busy in 1973. In addition to Ethernet, PARC developed the first personal computer that used a graphical user interface complete with icons, windows, and menus, and the world's first laser printer.) In 1979, Xerox began working with Intel and DEC (a once popular computer company) to make Ethernet an industry standard networking product. Along the way, they enlisted the help of the IEEE, which formed committee number 802.3 and began the process of standardizing Ethernet in 1981. The 802.3 committee released the first official Ethernet standard in 1983. Meanwhile, Bob Metcalfe left Xerox, turned down a job offer from Steve Jobs to work at Apple computers, and started a company called the Computer, Communication, and Compatibility Corporation — now known as 3Com. 3Com has since become one of the largest manufacturers of Ethernet equipment in the world. Gigabit Ethernet Gigabit Ethernet is Ethernet running at a whopping 1,000 Mbps, which is 100 times faster than the original 10 Mbps Ethernet. Gigabit Ethernet was once considerably more expensive than Fast Ethernet, so it was used only when the improved performance justified the extra cost. However, today Gigabit Ethernet is the standard for nearly all desktop and laptop PCs. Gigabit Ethernet comes in two flavors: ♦ 1000BaseT: Gigabit Ethernet can run on Category 5 UTP cable, but higher grades such as Category 5e or Category 6 are preferred because they're more reliable. ♦ 1000BaseLX: Several varieties of fiber cable are used with Gigabit Ethernet, but the most popular is called 1000BaseLX. The TCP/IP Protocol Suite
- 57. TCP/IP, the protocol on which the Internet is built, is actually not a single protocol but rather an entire suite of related protocols. TCP is even older than Ethernet. It was first conceived in 1969 by the Department of Defense. For more on the history of TCP/IP, see the sidebar, "The fascinating story of TCP/IP," later in this chapter. Currently, the Internet Engineering Task Force, or IETF, manages the TCP/IP protocol suite. The TCP/IP suite is based on a four-layer model of networking that is similar to the seven-layer OSI model. Figure 2-7 shows how the TCP/IP model matches up with the OSI model and where some of the key TCP/IP protocols fit into the model. As you can see, the lowest layer of the model, the Network Interface layer, corresponds to the OSI model's Physical and Data Link layers. TCP/IP can run over a wide variety of Network Interface layer protocols, including Ethernet, as well as other protocols, such as Token Ring and FDDI (an older standard for fiber-optic networks). Figure 2-7: TCP/IP and the OSI model. The Application layer of the TCP/IP model corresponds to the upper three layers of the OSI model — that is, the Session, Presentation, and Application layers. Many protocols can be used at this level. A few of the most popular are HTTP, FTP, Telnet, SMTP, DNS, and SNMP. You can find out about many of the details of these and other TCP/IP protocols in Book IV. In the following sections, I just want to point out a few more details of the three most important protocols in the TCP/IP suite: IP, TCP, and UDP. IP IP, which stands for Internet Protocol, is a Network layer protocol that is responsible for delivering packets to network devices. The IP protocol uses logical IP addresses to refer to individual devices rather than physical (MAC) addresses. A protocol called ARP (for Address Resolution Protocol) handles the task of converting IP addresses to MAC addresses. 10Base what? The names of Ethernet cable standards resemble the audible signals a quarterback might shout at the line of scrimmage. In reality, the cable designations consist of three parts: The first number is the speed of the network in Mbps. So 10BaseT is for 10 Mbps networks (Standard Ethernet), 100BaseTX is for 100 Mbps networks (Fast Ethernet), and 1000BaseT is for 1,000 Mbps networks (Gigabit Ethernet). The word Base indicates the type of network transmission that the cable uses. Base is short for baseband. Baseband transmissions carry one signal at a time and are relatively simple to implement. The alternative to baseband is broadband, which can carry more than one signal at a time but is more difficult to implement. At one time, broadband incarnations of the 802.x networking standards existed, but they have all but fizzled due to lack of use.
- 58. The tail end of the designation indicates the cable type. For coaxial cables, a number is used that roughly indicates the maximum length of the cable in hundreds of meters. 10Base5 cables can run up to 500 meters. 10Base2 cables can run up to 185 meters. (The IEEE rounded 185 up to 200 to come up with the name 10Base2.) If the designation ends with a T, twisted-pair cable is used. Other letters are used for other types of cables. Because IP addresses consist of a network part and a host part, IP is a routable protocol. As a result, IP can forward a packet to another network if the host is not on the current network. (The ability to route packets across networks is where IP gets its name. Aninternet is a series of two or more connected TCP/IP networks that can be reached by routing.) TCP TCP, which stands for Transmission Control Protocol, is a connection-oriented Transport layer protocol. TCP lets a device reliably send a packet to another device on the same network or on a different network. TCP ensures that each packet is delivered if at all possible. It does so by establishing a connection with the receiving device and then sending the packets. If a packet doesn't arrive, TCP resends the packet. The connection is closed only after the packet has been successfully delivered or an unrecoverable error condition has occurred. One key aspect of TCP is that it's always used for one-to-one communications. In other words, TCP allows a single network device to exchange data with another single network device. TCP isn't used to broadcast messages to multiple network recipients. Instead, the User Datagram Protocol (UDP) is used for that purpose. The fascinating story of TCP/IP Some people are fascinated by history. They subscribe to cable TV just to get the History Channel. If you're one of those history buffs, you may be interested in the following chronicle of TCP/IP's humble origins. (For maximum effect, play some melancholy violin music in the background as you read the rest of this sidebar.) In the summer of 1969, the four mop-topped singers from Liverpool were breaking up. The war in Vietnam was escalating. Astronauts Neil Armstrong and Buzz Aldrin walked on the moon. And the Department of Defense built a computer network called ARPANET to link its defense installations with several major universities throughout the United States. By the early 1970s, ARPANET was becoming difficult to manage. So it was split into two networks: one for military use, called MILNET, and the other for nonmilitary use. The nonmilitary network retained the name ARPANET. To link MILNET with ARPANET, a new method of connecting networks, called Internet Protocol or just IP for short, was invented. The whole purpose of IP was to enable these two networks to communicate with each other. Fortunately, the designers of IP realized that it wouldn't be too long before other networks wanted to join in the fun, so they designed IP to allow for more than two networks. In fact, their ingenious design allowed for tens of thousands of networks to communicate via IP. The decision was a fortuitous one, as the Internet quickly began to grow. By the mid-1980s, the original ARPANET reached its limits. Just in time, the National Science Foundation (NSF) decided to get into the game. NSF had built a network called NSFNET to link its huge supercomputers. NSFNET replaced ARPANET as the new background for the Internet. Around that time, such magazines as Time and Newsweek began writing articles about this new phenomenon called the Internet, and the Net (as it became nicknamed) began to grow like wildfire. Soon NSFNET couldn't keep up with the growth, so several private commercial networks took over management of the Internet backbone. The Internet has grown at a dizzying rate ever since, and nobody knows how long this frenetic growth rate will continue. One thing is sure: TCP/IP is now the most popular networking protocol in the world. Many well-known Application layer protocols rely on TCP. For example, when a user running a Web browser requests a page, the browser uses HTTP to send a request via TCP to the Web server. When the Web server receives the request, it uses HTTP to send the requested Web page back to the browser, again via TCP. Other Application layer protocols that use TCP include Telnet (for terminal emulation), FTP (for file exchange), and SMTP (for e-mail). UDP The User Datagram Protocol (or UDP) is a connectionless Transport layer protocol that is used when the overhead of a connection isn't required. After UDP has placed a packet on the network (via the IP protocol), it forgets about it. UDP doesn't guarantee that the packet actually arrives at its destination.
- 59. Most applications that use UDP simply wait for any replies expected as a result of packets sent via UDP. If a reply doesn't arrive within a certain period of time, the application either sends the packet again or gives up. Probably the best-known Application layer protocol that uses UDP is DNS, the Domain Name System. When an application needs to access a domain name such aswww.wiley.com, DNS sends a UDP packet to a DNS server to look up the domain. When the server finds the domain, it returns the domain's IP address in another UDP packet. (Actually, the process is much more complicated than that. For a more detailed explanation, see Book IV, Chapter 4.) Other Protocols Worth Knowing About Other networks besides Ethernet, TCP/IP, and IPX/SPX are worth knowing about: ♦ NetBIOS: Short for Network Basic Input/Output System, this is the basic application-programming interface for network services on Windows computers. It's installed automatically when you install TCP/IP, but doesn't show up as a separate protocol when you view the network connection properties. (Refer to Figure 2-1.) NetBIOS is a Session layer protocol that can work with Transport layer protocols such as TCP, SPX, or NetBEUI. ♦ NetBEUI: Short for Network BIOS Extended User Interface, this is a Transport layer protocol that was designed for early IBM and Microsoft networks. NetBEUI is now considered obsolete. ♦ IPX/SPX: A protocol suite that was made popular in the 1980s by Novell for use with their NetWare servers. TCP/IP has become so dominant that IPX/SPX is now only rarely used. ♦ AppleTalk: Apple computers have their own suite of network protocols known asAppleTalk. The AppleTalk suite includes a Physical and Data Link layer protocol calledLocalTalk, but can also work with standard lower-level protocols, including Ethernet and Token Ring. ♦ SNA: Systems Network Architecture is an IBM networking architecture that dates back to the 1970s, when mainframe computers roamed the earth and PCs had barely emerged from the primordial computer soup. SNA was designed primarily to support huge terminals such as airline reservation and banking systems, with tens of thousands of terminals attached to central host computers. Now that IBM mainframes support TCP/IP and terminal systems have all but vanished, SNA is beginning to fade away. Still, many networks that incorporate mainframe computers have to contend with SNA. Chapter 3: Understanding Network Hardware In This Chapter Introducing servers Working with network interface cards Becoming familiar with network cable, network hubs, and switches Exploring repeaters, bridges, and routers Figuring out network storage The building blocks of networks are network hardware devices such as servers, adapter cards, cables, hubs, switches, routers, and so on. This chapter provides an overview of these building blocks. Servers Server computers are the lifeblood of any network. Servers provide the shared resources that network users crave, such as file storage, databases, e-mail, Web services, and so on. Choosing the equipment you use for your network's servers is one of the key decisions you'll make when you set up a network. In the following sections, I describe some of the various ways you can equip your network's servers. Right off the bat, I want to make one thing clear: Only the smallest networks can do without at least one dedicated server computer. For a home network or a small office network with only a few computers, you can get away with true peer-to-peer networking. That's where each client computer shares its resources such as file storage or printers, and a dedicated server computer isn't needed. For a more-detailed explanation of why this isn't a good idea for larger networks, see Book II, Chapter 1. What's important in a server Here are some general things to keep in mind when picking a server computer for your network: ♦ Scalability: Scalability refers to the ability to increase the size and capacity of the server computer without unreasonable hassle. It's a major mistake to purchase a server computer that just meets your
- 60. current needs because, you can rest assured, your needs will double within a year. If at all possible, equip your servers with far more disk space, RAM, and processor power than you currently need. ♦ Reliability: The old adage "you get what you pay for" applies especially well to server computers. Why spend $10,000 on a server computer when you can buy one with seemingly similar specifications at a discount electronics store for $2,000? One reason is reliability. When a client computer fails, only the person who uses that computer is affected. When a server fails, however, everyone on the network is affected. The less-expensive computer is probably made of inferior components that are more likely to fail. ♦ Availability: This concept of availability is closely related to reliability. When a server computer fails, how long does it take to correct the problem and get the server up and running again? Server computers are designed so their components can be easily diagnosed and replaced, which minimizes the downtime that results when a component fails. In some servers, components are hot swappable, which means that certain components can be replaced without shutting down the server. Some servers are designed to be fault-tolerantso that they can continue to operate even if a major component fails. ♦ Service and support: Service and support are factors often overlooked when picking computers. If a component in a server computer fails, do you have someone on site qualified to repair the broken computer? If not, you should get an on-site maintenance contract for the computer. Don't settle for a maintenance contract that requires you to take the computer in to a repair shop or, worse, mail it to a repair facility. You can't afford to be without your server that long. Components of a server computer The hardware components that comprise a typical server computer are similar to the components used in less expensive client computers. However, server computers are usually built from higher-grade components than client computers for the reasons given in the preceding section. The following paragraphs describe the typical components of a server computer: ♦ Motherboard: The motherboard is the computer's main electronic circuit board to which all the other components of your computer are connected. More than any other component, the motherboard is the computer. All other components attach to the motherboard. The major components on the motherboard include the processor (or CPU), supporting circuitry called the chipset, memory, expansion slots, a standard IDE hard drive controller, and I/O ports for devices such as keyboards, mice, and printers. Some motherboards also include additional built-in features such as a graphic adapter, SCSI disk controller, or network interface. ♦ Processor: The processor, or CPU, is the brain of the computer. Although the processor isn't the only component that affects overall system performance, it's the one that most people think of first when deciding what type of server to purchase. At the time of this writing, Intel had two processor models specifically designed for use in server computers, as summarized in Table 3-1. Each motherboard is designed to support a particular type of processor. CPUs come in two basic mounting styles: slot or socket. However, you can choose from several types of slots and sockets, so you have to make sure that the motherboard supports the specific slot or socket style used by the CPU. Some server motherboards have two or more slots or sockets to hold two or more CPUs. The term clock speed refers to how fast the basic clock that drives the processor's operation ticks. In theory, the faster the clock speed, the faster the processor. However, clock speed alone is reliable only for comparing processors within the same family. In fact, the Itanium processors are faster than Xeon processors at the same clock speed. That's because the Itanium processor models contain more advanced circuitry than the older model, so they can accomplish more work with each tick of the clock. The number of processor cores also has a dramatic effect on performance. Each processor core acts as if it's a separate processor. Most server computers use dual-core (two processor cores) or quad-core (four cores) chips.
- 61. ♦ Memory: Don't scrimp on memory. People rarely complain about servers having too much memory. Many different types of memory are available, so you have to pick the right type of memory to match the memory supported by your motherboard. The total memory capacity of the server depends on the motherboard. Most new servers can support at least 16GB of memory, and some can handle up to 256GB. ♦ Hard drives: Most desktop computers use inexpensive hard drives called SATA drives.These drives are adequate for individual users, but because performance is more important for servers, another type of drive known as SCSI is usually used instead. For the best performance, use the SCSI drives along with a high-performance SCSI controller card. (However, because of its low cost, SATA drives are often used in inexpensive servers.) ♦ Network connection: The network connection is one of the most important parts of any server. Many servers have network adapters built into the motherboard. If your server isn't equipped as such, you'll need to add a separate network adapter card. See the section, "Network Interface Cards," later in this chapter, for more information. ♦ Video: Fancy graphics aren't that important for a server computer. You can equip your servers with inexpensive generic video cards and monitors without affecting network performance. (This is one of the few areas where it's acceptable to cut costs on a server.) ♦ Power supply: Because a server usually has more devices than a typical desktop computer, it requires a larger power supply (typically 300 watts). If the server houses a large number of hard drives, it may require an even larger power supply. Server form factors The term form factor refers to the size, shape, and packaging of a hardware device. Server computers typically come in one of three form factors: ♦ Tower case: Most servers are housed in a traditional tower case, similar to the tower cases used for desktop computers. A typical server tower case is 18-inches high, 20-inches deep, and 9-inches wide and has room inside for a motherboard, five or more hard drives, and other components. Tower cases also come with built-in power supplies. Some server cases include advanced features specially designed for servers, such as redundant power supplies (so both servers can continue operating if one of the power supplies fails), hot-swappable fans, and hot-swappable disk drive bays. (Hot-swappablecomponents can be replaced without powering down the server.) ♦ Rack mount: If you need only a few servers, tower cases are fine. You can just place the servers next to each other on a table or in a cabinet that's specially designed to hold servers. If you need more than a few servers, though, space can quickly become an issue. For example, what if your departmental network requires a bank of ten file servers? You'd need a pretty long table. Rack-mount servers are designed to save space when you need more than a few servers in a confined area. A rack-mount server is housed in a small chassis that's designed to fit into a standard 19-inch equipment rack. The rack allows you to vertically stack servers in order to save space. ♦ Blade servers: Blade servers are designed to save even more space than rack-mount servers. A blade server is a server on a single card that can be mounted alongside other blade servers in a blade chassis, which itself fits into a standard 19-inch equipment rack. A typical blade chassis holds six or more servers, depending on the manufacturer. One of the key benefits of blade servers is that you don't need a separate power supply for each server. Instead, the blade enclosure provides power for all its blade servers. Some blade server systems provide rack-mounted power supplies that can serve several blade enclosures mounted in a single rack.
- 62. In addition, the blade enclosure provides KVM switching so that you don't have to use a separate KVM switch. You can control any of the servers in a blade server network from a single keyboard, monitor, and mouse. (For more information, see the sidebar, "Saving space with a KVM switch.") One of the biggest benefits of blade servers is that they drastically cut down the amount of cable clutter. With rack-mount servers, each server requires its own power cable, keyboard cable, video cable, mouse cable, and network cables. With blade servers, a single set of cables can service all the servers in a blade enclosure. Saving space with a KVM switch If you have more than two or three servers in one location, you should consider getting a device called a KVM switch to save space. A KVM switch lets you connect several server computers to a single keyboard, monitor, and mouse. (KVM stands for keyboard, video, and mouse.) Then, you can control any of the servers from a single keyboard, monitor, and mouse by turning a dial or by pressing a button on the KVM switch. Simple KVM switches are mechanical affairs that let you choose from among 2 to 16 or more computers. More elaborate KVM switches can control more computers, using a pop-up menu or a special keyboard combination to switch among computers. Some advanced KVMs can even control a mix of PCs and Macintosh computers from a single keyboard, monitor, and mouse. To find more information about KVM switches, go to a Web search engine such as Google and search for "KVM." Network Interface Cards Every computer on a network, both clients and servers, requires a network interface card (or NIC) in order to access the network. A NIC is usually a separate adapter card that slides into one of the server's motherboard expansion slots. However, most newer computers have the NIC built into the motherboard, so a separate card isn't needed. For client computers, you can usually get away with using the inexpensive built-in NIC because client computers are used to connect only one user to the network. However, the NIC in a server computer connects many network users to the server. As a result, it makes sense to spend more money on a higher- quality NIC for a heavily used server. Most network administrators prefer to use name-brand cards from manufacturers such as Intel, SMC, or 3Com. Most NICs made today support 1 Gbps networking and will also support slower 100 Mbps and even ancient 10 Mbps networks. These cards automatically adjust their speed to match the speed of the network. So you can use a gigabit card on a network that has older 100 Mbps cards without trouble. You can find inexpensive gigabit cards for as little as $5 each, but a typical name-brand card (such as Linksys or Intel) will cost around $25 or $30. Here are a few other points to ponder concerning network interface cards: ♦ A NIC is a Physical layer and Data Link layer device. Because a NIC establishes a network node, it must have a physical network address, also known as a MAC address. The MAC address is burned into the NIC at the factory, so you can't change it. Every NIC ever manufactured has a unique MAC address. ♦ For server computers, it makes sense to use more than one NIC. That way, the server can handle more network traffic. Some server NICs have two or more network interfaces built into a single card. ♦ Fiber-optic networks also require NICs. Fiber-optic NICs are still too expensive for desktop use in most networks. Instead, they're used for high-speed backbones. If a server connects to a high-speed fiber backbone, it will need a fiber-optic NIC that matches the fiber-optic cable being used. Network Cable Nearly all modern networks are constructed using a type of cable called twisted-pair cable, which looks a little like phone cable but is subtly different. You may encounter other types of cable in an existing network: coax cable that resembles TV cable, thick yellow cable that used to be the only type of cable used for Ethernet, fiber-optic cables that span long distances at high speeds, or thick twisted-pair bundles that carry multiple sets of twisted-pair cable between wiring closets in a large building. But as I mentioned, it's twisted-pair cable for nearly all new networks.
- 63. A choice that's becoming more popular every day is to forego network cable and instead build your network using wireless network components. Because Book V is devoted exclusively to wireless networking, I don't describe wireless network components in this chapter. Coaxial cable A type of cable that was once popular for Ethernet networks is coaxial cable, sometimes called thinnet or BNC cable because of the type of connectors used on each end of the cable. Thinnet cable operates only at 10 Mbps and is rarely used for new networks. However, you'll find plenty of existing thinnet networks still being used. Figure 3-1 shows a typical coaxial cable. Figure 3-1: Coax cable. Here are some salient points about coaxial cable: ♦ You attach thinnet to the network interface card by using a goofy twist-on connector called a BNC connector. You can purchase preassembled cables with BNC connectors already attached in lengths of 25 or 50 feet, or you can buy bulk cable on a big spool and attach the connectors yourself by using a special tool. (I suggest buying preassembled cables. Attaching connectors to bulk cable can be tricky.) ♦ With coaxial cables, you connect your computers point-to-point in a bus topology. At each computer, a T connector is used to connect two cables to the network interface card. ♦ A special plug called a terminator is required at each end of a series of thinnet cables. The terminator prevents data from spilling out the end of the cable and staining the carpet. ♦ The cables strung end-to-end from one terminator to the other are collectively called asegment. The maximum length of a thinnet segment is about 200 meters (actually, 185 meters). You can connect as many as 30 computers on one segment. To span a distance greater than 185 meters or to connect more than 30 computers, you must use two or more segments with a device called a repeater to connect each segment.
- 64. ♦ Although Ethernet coaxial cable resembles TV coaxial cable, the two types of cable aren't interchangeable. Don't try to cut costs by wiring your network with cheap TV cable. Twisted-pair cable The most popular type of cable today is twisted-pair cable, or UTP. (The U stands for unshielded, but no one says unshielded twisted pair. Just twisted pair will do.) UTP cable is even cheaper than thin coaxial cable, and best of all, many modern buildings are already wired with twisted-pair cable because this type of wiring is often used with modern phone systems. Figure 3-2 shows a twisted-pair cable. Figure 3-2: Twisted-pair cable. When you use UTP cable to construct an Ethernet network, you connect the computers in a star arrangement. In the center of the star is a device called a hub. Depending on the model, Ethernet hubs enable you to connect from 4 to 24 computers using twisted-pair cable. An advantage of UTP's star arrangement is that if one cable goes bad, only the computer attached to that cable is affected; the rest of the network continues to chug along. With coaxial cable, a bad cable affects the entire network, and not just the computer to which the bad cable is connected. Here are a few other details that you should know about twisted-pair cabling: ♦ UTP cable consists of pairs of thin wire twisted around each other; several such pairs are gathered up inside an outer insulating jacket. Ethernet uses two pairs of wires, or four wires altogether. The number of pairs in a UTP cable varies, but it's often more than two. ♦ UTP cable comes in various grades called Categories. Don't use anything less than Category 5e cable for your network. Although cheaper, it may not be able to support faster networks. Although higher-Category cables are more expensive than lower-Category cables, the real cost of installing Ethernet cabling is the labor required to actually pull the cables through the walls. As a result, I recommend that you always spend the extra money to buy Category 5e cable. ♦ If you want to sound like you know what you're talking about, say "Cat 5e" instead of "Category 5e." ♦ Many existing networks are cabled with Category 5 cable, which is fine for 100Mbps networks but isn't rated for Gigabit networks. Category 5e cable (the e stands for enhanced) and Category 6 cable will support 1,000 Mbps networks. ♦ UTP cable connectors look like modular phone connectors but are a bit larger. UTP connectors are officially called RJ-45 connectors. ♦ Like thinnet cable, UTP cable is also sold in prefabricated lengths. However, RJ-45 connectors are much easier to attach to bulk UTP cable than BNC cables are to attach to bulk coaxial cable. As a result, I suggest
- 65. that you buy bulk cable and connectors unless your network consists of just two or three computers. A basic crimp tool to attach the RJ-45 connectors costs about $50. ♦ The maximum allowable cable length between the hub and the computer is 100 meters (about 328 feet). Switches The biggest difference between using coaxial cable and twisted-pair cable is that when you use twisted- pair cable, you also must use a separate device called a switch. Years ago, switches were expensive devices — expensive enough that most do-it-yourself networkers who were building small networks opted for thinnet cable in order to avoid the expense and hassle of using hubs. Nowadays, the cost of switches has dropped so much that the advantages of twisted-pair cabling outweigh the hassle and cost of using switches. With twisted-pair cabling, you can more easily add new computers to the network, move computers, find and correct cable problems, and service the computers that you need to remove from the network temporarily. Note that in some older networks, you may see a device known as a hub used instead of a switch. Hubs used to be used because they were less expensive than switches. However, the cost of switches came down dramatically, pushing hubs into relic status. If you have an older network that uses hubs and seems to run slowly, you can probably improve the network's speed by replacing the older hubs with newer switches. For more information, see the sidebar, "Hubs and switches demystified," later in this chapter. Hubs and switches demystified Both hubs and switches let you connect multiple computers to a twisted-pair network. Switches are more efficient than hubs, but not just because they're faster. If you really want to know, here's the actual difference between a hub and a switch: In a hub, every packet that arrives at the hub on any of its ports is automatically sent out on every other port. The hub has to do this because it's a Physical layer device, so it has no way to keep track of which computer is connected to each port. For example, suppose that John's computer is connected to port 1 on an 8-port hub, and Andrea's computer is connected to port 5. If John's computer sends a packet of information to Andrea's computer, the hub receives the packet on port 1 and then sends it out on ports 2-8. All the computers connected to the hub get to see the packet so that they can determine whether the packet was intended for them. A switch is a Data Link layer device, which means it's able to look into the packets that pass through it to examine a critical piece of Data Link layer information: the MAC address. With this information in hand, a switch can keep track of which computer is connected to each of its ports. So if John's computer on port 1 sends a packet to Andrea's computer on port 5, the switch receives the packet on port 1 and then sends the packet out on port 5 only. This process is not only faster, but also improves the security of the system because other computers don't see packets that aren't meant for them. If you use twisted-pair cabling, you need to know some of the ins and outs of using hubs: ♦ Because you must run a cable from each computer to the switch, find a central location for the switch to which you can easily route the cables. ♦ The switch requires electrical power, so make sure that an electrical outlet is handy. ♦ When you purchase a switch, purchase one with at least twice as many connections as you need. Don't buy a four-port switch if you want to network four computers because when (not if) you add the fifth computer, you have to buy another switch. ♦ You can connect switches to one another, as shown in Figure 3-3; this is called daisy chaining. When you daisy chain switches, you connect one end of a cable to a port on one switch and the other end to a port on the other switch. Note that on some switches, you must use a special designated port for daisy chaining. So be sure to read the instructions that come with the switch to make sure that you daisy chain it properly. Figure 3-3: Daisy chaining switches together.
- 67. ♦ You can daisy chain no more than three switches together. If you have more computers than three hubs can accommodate, don't panic. For a small additional cost, you can purchase hubs that have a BNC connection on the back. Then you can string the hubs together using thinnet cable. The three-hub limit doesn't apply when you use thinnet cable to connect the hubs. You can also get stackable switches that have high-speed direct connections that enable two or more switches to be counted as a single switch. ♦ When you shop for network hubs, you may notice that the expensive ones have network-management features that support something called SNMP. These hubs are calledmanaged hubs. Unless your network is very large and you know what SNMP is, don't bother with the more expensive managed hubs. You'd be paying for a feature that you may never use. ♦ For large networks, you may want to consider using a managed switch. A managed switch allows you to monitor and control various aspects of the switch's operation from a remote computer. The switch can alert you when something goes wrong with the network, and it can keep performance statistics so that you can determine which parts of the network are heavily used and which aren't. A managed switch costs two or three times as much as an unmanaged switch, but for larger networks, the benefits of managed switches are well worth the additional cost. Repeaters A repeater (sometimes called an extender) is a gizmo that gives your network signals a boost so that the signals can travel farther. It's kind of like a Gatorade station in a marathon. As the signals travel past the repeater, they pick up a cup of Gatorade, take a sip, splash the rest of it on their heads, toss the cup, and hop in a cab when they're sure that no one is looking. You need a repeater when the total length of a single span of network cable exceeds 100 meters (328 feet). The 100-meter length limit applies to the cable that connects a computer to the switch or the cable that connects switches to each other when switches are daisy chained together. In other words, you can connect each computer to the switch with no more than 100 meters of cable, and you can connect switches to each other with no more than 100 meters of cable. Figure 3-4 shows how you can use a repeater to connect two groups of computers that are too far apart to be strung on a single segment. When you use a repeater like this, the repeater divides the cable into two segments. The cable length limit still applies to the cable on each side of the repeater. Here are some points to ponder when you lie awake tonight wondering about repeaters: ♦ Repeaters are not typically used with twisted-pair networks. Well, technically, that's not true because the switches themselves function as repeaters. So what I really meant is that you typically see repeaters as stand-alone devices only when a single cable segment would be more than 100 meters. ♦ A basic rule of Ethernet life is that a signal can't pass through more than three repeaters on its way from one node to another. That doesn't mean you can't have more than three repeaters or switches, but if you do, you have to carefully plan the network cabling so that the three-repeater rule isn't violated. ♦ Repeaters are legitimate components of a by-the-book Ethernet network. They don't extend the maximum length of a single segment; they just enable you to tie two segments together. Beware of the little black boxes that claim to extend the segment limit beyond the standard 100-meter limit for 10/100BaseT cable. These products usually work, but playing by the rules is better. Figure 3-4: Using a repeater.
- 68. Bridges A bridge is a device that connects two networks so that they act as if they're one network. Bridges are used to partition one large network into two smaller networks for performance reasons. You can think of a bridge as a kind of smart repeater. Repeaters listen to signals coming down one network cable, amplify them, and send them down the other cable. They do this blindly, paying no attention to the content of the messages that they repeat. In contrast, a bridge is a little smarter about the messages that come down the pike. For starters, most bridges have the capability to listen to the network and automatically figure out the address of each computer on both sides of the bridge. Then the bridge can inspect each message that comes from one side of the bridge and broadcast it on the other side of the bridge, but only if the message is intended for a computer that's on the other side. This key feature enables bridges to partition a large network into two smaller, more efficient networks. Bridges work best in networks that are highly segregated. For example (humor me here — I'm a Dr. Seuss fan), suppose that the Sneetches networked all their computers and discovered that, although the Star- Bellied Sneetches' computers talked to each other frequently and the Plain-Bellied Sneetches' computers also talked to each other frequently, rarely did a Star-Bellied Sneetch's computer talk to a Plain-Bellied Sneetch's computer.
- 69. A bridge can partition the Sneetchnet into two networks: the Star-Bellied network and the Plain-Bellied network. The bridge automatically learns which computers are on the Star-Bellied network and which are on the Plain-Bellied network. The bridge forwards messages from the Star-Bellied side to the Plain-Bellied side (and vice versa) only when necessary. The overall performance of both networks improves, although the performance of any network operation that has to travel over the bridge slows down a bit. Here are a few additional things to consider about bridges: ♦ Some bridges also have the capability to translate the messages from one format to another. For example, if the Star-Bellied Sneetches build their network with Ethernet and the Plain-Bellied Sneetches use Token Ring, a bridge can tie the two together. ♦ You can get a basic bridge to partition two Ethernet networks for about $500 from mail order suppliers. More sophisticated bridges can cost as much as $5,000 or more. ♦ For simple bridge applications, you don't need an expensive specialized bridge device; instead, you can just use a switch. That's because a switch is effectively a multi-port bridge. ♦ If you've never read Dr. Seuss's classic story of the Sneetches, you should. Routers A router is like a bridge, but with a key difference. Bridges are Data Link layer devices, so they can tell the MAC address of the network node to which each message is sent, and can forward the message to the appropriate segment. However, they can't peek into the message itself to see what type of information is being sent. In contrast, a router is a Network layer device, so it can work with the network packets at a higher level. In particular, a router can examine the IP address of the packets that pass through it. And because IP addresses have both a network and a host address, a router can determine what network a message is coming from and going to. Bridges are ignorant of this information. One key difference between a bridge and a router is that a bridge is essentially transparent to the network. In contrast, a router is itself a node on the network, with its own MAC and IP addresses. This means that messages can be directed to a router, which can then examine the contents of the message to determine how it should handle the message. You can configure a network with several routers that can work cooperatively together. For example, some routers are able to monitor the network to determine the most efficient path for sending a message to its ultimate destination. If a part of the network is extremely busy, a router can automatically route messages along a less-busy route. In this respect, the router is kind of like a traffic reporter up in a helicopter. The router knows that the 101 is bumper-to-bumper all the way through Sunnyvale, so it sends the message on 280 instead. Here's some additional information about routers: ♦ The functional distinctions between bridges and routers — and switches and hubs, for that matter — get blurrier all the time. As bridges, hubs, and switches become more sophisticated, they're able to take on some of the chores that used to require a router, thus putting many routers out of work. ♦ Some routers are nothing more than computers with several network interface cards and special software to perform the router functions. ♦ Routers can also connect networks that are geographically distant from each other via a phone line (using modems) or ISDN. ♦ You can also use a router to join your LAN to the Internet. Figure 3-5 shows a router used for this purpose. Figure 3-5: Connecting to the Internet with a router.
- 70. Network Attached Storage Many network servers exist solely for the purpose of making disk space available to network users. As networks grow to support more users, and users require more disk space, network administrators are constantly finding ways to add more storage to their networks. One way to do that is to add more file servers. However, a simpler and less expensive way is to use network attached storage, also known as NAS. A NAS device is a self-contained file server that's preconfigured and ready to run. All you have to do to set it up is take it out of the box, plug it in, and turn it on. NAS devices are easy to set up and configure, easy to maintain, and less expensive than traditional file servers. NAS should not be confused with a related technology called storage area networks, or SAN. SAN is a much more complicated and expensive technology that provides huge quantities of data storage for large networks. For more information on SAN, see the sidebar, "SAN is NAS spelled backwards." A typical entry-level NAS device is the Dell PowerVault NX300. This device is a self-contained file server built into a small rack-mount chassis. It supports up to four hard drives with a total capacity up to four terabyte (or 4,000GB). The NX300 uses a Xeon processor and two built-in gigabit network ports. SAN is NAS spelled backwards
- 71. It's easy to confuse the terms storage area network (SAN) and network attached storage(NAS). Both refer to relatively new network technologies that let you manage the disk storage on your network. However, NAS is a much simpler and less expensive technology. A NAS device is nothing more than an inexpensive self-contained file server. Using NAS devices actually simplifies the task of adding storage to a network because the NAS eliminates the chore of configuring a network operating system for routine file- sharing tasks. A storage area network is designed for managing very large amounts of network storage — sometimes downright huge amounts. A SAN consists of three components: storage devices (perhaps hundreds of them), a separate high-speed network (usually fiber-optic) that directly connects the storage devices to each other, and one or more SAN servers that connect the SAN to the local area network. The SAN server manages the storage devices attached to the SAN and allows users of the LAN to access the storage. Setting up and managing a storage area network is a job for a SAN expert. For more information about storage area networks, see the home page of the Storage Networking Industry Association at www.snia.org. The Dell NX300 runs a special version of Windows Server 2008 called the Windows Storage Server 2008. This version of Windows is designed specifically for NAS devices. It allows you to configure the network storage from any computer on the network by using a Web browser. Note that some NAS devices use customized versions of Linux rather than Windows Storage Server. Also, in some systems, the operating system resides on a separate hard drive that's isolated from the shared disks. This prevents the user from inadvertently damaging the operating system. Network Printers Although you can share a printer on a network by attaching the printer to a server computer, many printers have network interfaces built in. This lets you connect the printer directly to the network. Then network users can connect to the printer and use it without going through a server. Even if you connect a printer directly to the network, it's still a good idea to have the printer managed by a server computer running a network operating system such as Windows Server 2003 or 2007. That way, the server can store print jobs sent to the printer by multiple users and print the jobs in the order in which they were received. Chapter 4: Understanding Network Operating Systems In This Chapter Understanding what network operating systems do Figuring out the advantages of Windows Server 2003 Analyzing Windows 2000 Server Taking a look at Windows NT Server Navigating NetWare Delving into peer-to-peer networking Exploring other network operating systems One of the basic choices that you must make before you proceed any further is to decide which network operating system (NOS) to use as the foundation for your network. This chapter begins with a description of several important features found in all network operating systems. Next, it provides an overview of the advantages and disadvantages of the most popular network operating systems. Network Operating System Features All network operating systems, from the simplest to the most complex, must provide certain core functions. These include the ability to connect to other computers on the network, share files and other resources, provide for security, and so on. In the following sections, I describe some of these core NOS features in general terms. Network support It goes without saying that a network operating system should support networks. (I can picture Mike Myers in his classic Saturday Night Live role as Linda Richman, host ofCoffee Talk, saying "I'm getting a little verklempt. . . . Talk amongst yourselves. . . . I'll give you a topic — network operating systems do not network, nor do they operate. Discuss.") A network operating system must support a wide variety of networking protocols in order to meet the needs of its users. That's because a large network typically consists of a mixture of various versions of
- 72. Windows, as well as a few scattered Macintosh (mostly in the art department) and possibly some Linux computers. The computers often have distinct protocols. Many servers have more than one network interface card installed. In that case, the NOS must be able to support multiple network connections. Ideally, the NOS should have the ability to balance the network load among its network interfaces. In addition, in the event that one of the connections fails, the NOS should be able to seamlessly switch to another connection. Finally, most network operating systems include a built-in ability to function as a router that connects two networks. The NOS router functions should also include firewall features in order to keep unauthorized packets from entering the local network. File-sharing services One of the most important functions of a network operating system is its ability to share resources with other network users. The most common resource that's shared is the server's file system. A network server must be able to share some or all of its disk space with other users so that those users can treat the server's disk space as an extension of their own computers' disk spaces. The NOS allows the system administrator to determine which portions of the server's file system to share. Although an entire hard drive can be shared, it isn't commonly done. Instead, individual directories or folders are shared. The administrator can control which users are allowed to access each shared folder. Because file sharing is the reason many network servers exist, network operating systems have more sophisticated disk management features than are found in desktop operating systems. For example, most network operating systems have the ability to manage two or more hard drives as if they were a single drive. In addition, most can create mirrors, which automatically keep backup copies of drives on a second drive. Multitasking Only one user at a time uses a desktop computer; however, multiple users simultaneously use server computers. As a result, a network operating system must provide support for multiple users who access the server remotely via the network. At the heart of multiuser support is multitasking, which is the ability of an operating system to execute more than one program — called a task or a process — at a time. Multitasking operating systems are like the guy who used to spin plates balanced on sticks on the old Ed Sullivan Show. He'd run from plate to plate, trying to keep them all spinning so they wouldn't fall off the sticks. To make it challenging, he'd do it blindfolded or riding on a unicycle. Although multitasking creates the appearance that two or more programs are executing on the computer at one time, in reality, a computer with a single processor can execute only one program at a time. The operating system switches the CPU from one program to another to create the appearance that several programs are executing simultaneously, but at any given moment, only one of the programs is actually executing. The others are patiently waiting for their turns. (However, if the computer has more than one CPU, the CPUs can execute programs simultaneously, which is called multiprocessing.) To see multitasking in operation on a Windows computer, press Ctrl+Alt+Delete to bring up the Windows Task Manager and then click the Processes tab. All the tasks currently active on the computer appear. For multitasking to work reliably, the network operating system must completely isolate the executing programs from each other. Otherwise, one program may perform an operation that adversely affects another program. Multitasking operating systems do this by providing each task with its own unique address space that makes it almost impossible for one task to affect memory that belongs to another task. In most cases, each program executes as a single task or process within the memory address space allocated to the task. However, a single program can also be split into several tasks. This technique is usually called multithreading, and the program's tasks are called threads. The two approaches to multitasking are preemptive and non-preemptive. Inpreemptive multitasking, the operating system decides how long each task gets to execute before it should step aside so that another task can execute. When a task's time is up, the operating system's task manager interrupts
- 73. the task and switches to the next task in line. All the network operating systems in widespread use today use preemptive multitasking. The alternative to preemptive multitasking is non-preemptive multitasking. In non-preemptive multitasking, each task that gets control of the CPU is allowed to run until it voluntarily gives up control so that another task can run. Non-preemptive multitasking requires less operating system overhead because the operating system doesn't have to keep track of how long each task has run. However, programs have to be carefully written so that they don't hog the computer all to themselves. Directory services Directories are everywhere. When you need to make a phone call, you look up the number in a phone directory. When you need to find the address of a client, you look up his or her name in your Rolodex. And when you need to find the Sam Goody store at a shopping mall, you look for the mall directory. Networks have directories, too. Network directories provide information about the resources that are available on the network, such as users, computers, printers, shared folders, and files. Directories are an essential part of any network operating system.
- 74. CompTIA Network+ N10-005 Authorized Cert Guide
- 75. Contents at a Glance Introduction CHAPTER 1 Introducing Computer Networks CHAPTER 2 Dissecting the OSI Model CHAPTER 3 Identifying Network Components CHAPTER 4 Understanding Ethernet CHAPTER 5 Working with IP Addresses CHAPTER 6 Routing Traffic CHAPTER 7 Introducing Wide-Area Networks CHAPTER 8 Connecting Wirelessly CHAPTER 9 Optimizing Network Performance CHAPTER 10 Using Command-Line Utilities CHAPTER 11 Managing a Network CHAPTER 12 Securing a Network CHAPTER 13 Troubleshooting Network Issues CHAPTER 14 Final Preparation APPENDIX A Answers to Review Questions APPENDIX B CompTIA Network+ N10-005 Exam Updates, Version 1.0 Glossary Index APPENDIX C Memory Tables (DVD Only) APPENDIX D Memory Table Answer Key (DVD Only) Table of Contents Introduction Chapter 1 Introducing Computer Networks Foundation Topics Defining a Network The Purpose of Networks Overview of Network Components Networks Defined by Geography LAN WAN Other Categories of Networks CAN MAN PAN Networks Defined by Topology Physical Versus Logical Topology Bus Topology Ring Topology
- 76. Star Topology Hub-and-Spoke Topology Full-Mesh Topology Partial-Mesh Topology Networks Defined by Resource Location Client-Server Networks Peer-to-Peer Networks Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 2 Dissecting the OSI Model Foundation Topics The Purpose of Reference Models The OSI Model Layer 1: The Physical Layer Layer 2: The Data Link Layer Media Access Control Logical Link Control Layer 3: The Network Layer Layer 4: The Transport Layer Layer 5: The Session Layer Layer 6: The Presentation Layer Layer 7: The Application Layer The TCP/IP Stack Layers of the TCP/IP Stack Common Application Protocols in the TCP/IP Stack Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 3 Identifying Network Components Foundation Topics Media Coaxial Cable Twisted-Pair Cable Shielded Twisted Pair Unshielded Twisted Pair
- 77. Plenum Versus Non-Plenum Cable Fiber-Optic Cable Multimode Fiber Single-Mode Fiber Cable Distribution Wireless Technologies Network Infrastructure Devices Hubs Bridges Switches Multilayer Switches Routers Infrastructure Device Summary Specialized Network Devices VPN Concentrators Firewalls DNS Servers DHCP Servers Proxy Servers Content Engines Content Switches Virtual Network Devices Virtual Servers Virtual Switches Virtual Desktops Other Virtualization Solutions Voice over IP Protocols and Components Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 4 Understanding Ethernet Foundation Topics Principles of Ethernet Ethernet Origins Carrier Sense Multiple Access Collision Detect Distance and Speed Limitations Ethernet Switch Features Virtual LANs Trunks
- 78. Spanning Tree Protocol Corruption of a Switch’s MAC Address Table Broadcast Storms STP Operation Link Aggregation Power over Ethernet Port Monitoring User Authentication First-Hop Redundancy Other Switch Features Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 5 Working with IP Addresses Foundation Topics Binary Numbering Principles of Binary Numbering Converting a Binary Number to a Decimal Number Converting a Decimal Number to a Binary Number Binary Numbering Practice Binary Conversion Exercise #1 Binary Conversion Exercise #1: Solution Binary Conversion Exercise #2 Binary Conversion Exercise #2: Solution Binary Conversion Exercise #3 Binary Conversion Exercise #3: Solution Binary Conversion Exercise #4 Binary Conversion Exercise #4: Solution IPv4 Addressing IPv4 Address Structure Classes of Addresses Types of Addresses Unicast Broadcast Multicast Assigning IPv4 Addresses IP Addressing Components Static Configuration Dynamic Configuration
- 79. BOOTP DHCP Automatic Private IP Addressing Subnetting Purpose of Subnetting Subnet Mask Notation Subnet Notation: Practice Exercise #1 Subnet Notation: Practice Exercise #1 Solution Subnet Notation: Practice Exercise #2 Subnet Notation: Practice Exercise #2 Solution Extending a Classful Mask Borrowed Bits Calculating the Number of Created Subnets Calculating the Number of Available Hosts Basic Subnetting Practice: Exercise #1 Basic Subnetting Practice: Exercise #1 Solution Basic Subnetting Practice: Exercise #2 Basic Subnetting Practice: Exercise #2 Solution Calculating New IP Address Ranges Advanced Subnetting Practice: Exercise #1 Advanced Subnetting Practice: Exercise #1 Solution Advanced Subnetting Practice: Exercise #2 Advanced Subnetting Practice: Exercise #2 Solution Additional Practice Classless Inter-Domain Routing IP Version 6 Need for IPv6 IPv6 Address Structure IPv6 Data Flows Unicast Multicast Anycast Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 6 Routing Traffic Foundation Topics Basic Routing Processes Sources of Routing Information
- 80. Directly Connected Routes Static Routes Dynamic Routing Protocols Routing Protocol Characteristics Believability of a Route Metrics Interior Versus Exterior Gateway Protocols Route Advertisement Method Distance Vector Link State Routing Protocol Examples Address Translation NAT PAT Multicast Routing IGMP PIM PIM-DM PIM-SM Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 7 Introducing Wide-Area Networks Foundation Topics WAN Properties WAN Connection Types WAN Data Rates WAN Media Types Physical Media Wireless Media WAN Technologies Dedicated Leased Line T1 E1 T3 E3 CSU/DSU Point-to-Point Protocol Digital Subscriber Line
- 81. Cable Modem Synchronous Optical Network Satellite Plain Old Telephone Service Integrated Services Digital Network Frame Relay Asynchronous Transfer Mode Multiprotocol Label Switching Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 8 Connecting Wirelessly Foundation Topics Introducing Wireless LANs WLAN Concepts and Components Wireless Routers Wireless Access Point Antennas Frequencies and Channels CSMA/CA Transmission Methods WLAN Standards 802.11a 802.11b 802.11g 802.11n Deploying Wireless LANs Types of WLANs IBSS BSS ESS Sources of Interference Wireless AP Placement Securing Wireless LANs Security Issues Approaches to WLAN Security Security Standards WEP WPA
- 82. WPA2 Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 9 Optimizing Network Performance Foundation Topics High Availability High-Availability Measurement Fault-Tolerant Network Design Hardware Redundancy Layer 3 Redundancy Design Considerations for High-Availability Networks High-Availability Best Practices Content Caching Load Balancing QoS Technologies Introduction to QoS QoS Configuration Steps QoS Components QoS Mechanisms Classification Marking Congestion Management Congestion Avoidance Policing and Shaping Link Efficiency Case Study: SOHO Network Design Case Study Scenario Suggested Solution IP Addressing Layer 1 Media Layer 2 Devices Layer 3 Devices Wireless Design Environmental Factors Cost Savings Versus Performance Topology Summary Exam Preparation Tasks
- 83. Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 10 Using Command-Line Utilities Foundation Topics Windows Commands arp ipconfig nbtstat netstat nslookup ping route tracert UNIX Commands arp dig and nslookup host ifconfig traceroute netstat ping Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 11 Managing a Network Foundation Topics Maintenance Tools Bit-Error Rate Tester Butt Set Cable Certifier Cable Tester Connectivity Software Crimper Electrostatic Discharge Wrist Strap Environmental Monitor Loopback Plug Multimeter
- 84. Protocol Analyzer Punch-Down Tool Throughput Tester Time Domain Reflectometer/Optical Time Domain Reflectometer Toner Probe Configuration Management Monitoring Resources and Reports SNMP Syslog Logs Application Logs Security Logs System Logs Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 12 Securing a Network Foundation Topics Security Fundamentals Network Security Goals Confidentiality Integrity Availability Categories of Network Attacks Confidentiality Attacks Integrity Attacks Availability Attacks Defending Against Attacks User Training Patching Security Policies Governing Policy Technical Policies End User Policies More Detailed Documents Incident Response Vulnerability Scanners Nessus Nmap
- 85. Honey Pots and Honey Nets Access Control Lists Remote Access Security Firewalls Firewall Types Firewall Inspection Types Packet-Filtering Firewall Stateful Firewall Firewall Zones Virtual Private Networks Overview of IPsec IKE Modes and Phases Authentication Header and Encapsulating Security Payload The Five Steps in Setting Up and Tearing Down an IPsec Site-to-Site VPN Other VPN Technologies Intrusion Detection and Prevention IDS Versus IPS IDS and IPS Device Categories Detection Methods Deploying Network-Based and Host-Based Solutions Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 13 Troubleshooting Network Issues Foundation Topics Troubleshooting Basics Troubleshooting Fundamentals Structured Troubleshooting Methodology Physical Layer Troubleshooting Physical Layer Troubleshooting: Scenario Physical Layer Troubleshooting: Solution Data Link Layer Troubleshooting Data Link Layer Troubleshooting: Scenario Data Link Layer Troubleshooting: Solution Network Layer Troubleshooting Layer 3 Data Structures Common Layer 3 Troubleshooting Issues Network Layer Troubleshooting: Scenario Network Layer Troubleshooting: Solution
- 86. Wireless Troubleshooting Wireless Network Troubleshooting: Scenario Wireless Network Troubleshooting: Solution Summary Exam Preparation Tasks Review All the Key Topics Complete Tables and Lists from Memory Define Key Terms Review Questions Chapter 14 Final Preparation Tools for Final Preparation Pearson Cert Practice Test Engine and Questions on the DVD Install the Software from the DVD Activate and Download the Practice Exam Activating Other Exams Premium Edition Video Training on DVD Memory Tables End-of-Chapter Review Tools Suggested Plan for Final Review and Study Summary APPENDIX A Answers to Review Questions APPENDIX B CompTIA Network+ N10-005 Exam Updates, Version 1.0 Glossary Index APPENDIX C Memory Tables (DVD Only) APPENDIX D Memory Table Answer Key (DVD Only) Reader Services Visit our website and register this book atwww.pearsonitcertification.com/title/9780789748218 for convenient access to any updates, downloads, or errata that might be available for this book. CompTIA Network+ The CompTIA Network+ (2011 Edition) certification ensures that the successful candidate has the important knowledge and skills necessary to manage, maintain, troubleshoot, install, operate, and configure basic network infrastructure, describe networking technologies, basic design principles, and adhere to wiring standards and use testing tools. It Pays to Get Certified
- 87. In a digital world, digital literacy is an essential survival skill— Certification proves you have the knowledge and skill to solve business problems in virtually any business environment. Certifications are highly valued credentials that qualify you for jobs, increased compensation, and promotion. CompTIA Network+ certification held by many IT staff in organizations—21% of IT staff within a random sampling of U.S. organizations within a cross section of industry verticals hold Network+ certification. • The CompTIA Network+ credential—Proves knowledge of networking features and functions and is the leading vendor-neutral certification for networking professionals. • Starting Salary—The average starting salary of network engineers can be up to $70,000. • Career Pathway—CompTIA Network+ is the first step in starting a networking career and is recognized by Microsoft as part of their MS program. Other corporations, such as Novell, Cisco, and HP, also recognize CompTIA Network+ as part of their certification tracks. • More than 260,000—Individuals worldwide are CompTIA Network+ certified. • Mandated/recommended by organizations worldwide—Such as Cisco, HP, Ricoh, the U.S. State Department, and U.S. government contractors such as EDS, General Dynamics, and Northrop Grumman. How Certification Helps Your Career CompTIA Career Pathway CompTIA offers a number of credentials that form a foundation for your career in technology and allow you to pursue specific areas of concentration. Depending on the path you choose to take, CompTIA certifications help you
- 88. build upon your skills and knowledge, supporting learning throughout your entire career. Join the Professional Community
- 89. Content Seal of Quality This courseware bears the seal of CompTIA Approved Quality Content. This seal signifies this content covers 100% of the exam objectives and implements important instructional design principles. CompTIA recommends multiple learning tools to help increase coverage of the learning objectives. Why CompTIA? • Global Recognition—CompTIA is recognized globally as the leading IT non-profit trade association and has enormous credibility. Plus, CompTIA’s certifications are vendor-neutral and offer proof of foundational knowledge that translates across technologies. • Valued by Hiring Managers—Hiring managers value CompTIA certification, because it is vendor- and technology-independent validation of your technical skills. • Recommended or Required by Government and Businesses—Many government organizations and corporations either recommend or require technical staff to be CompTIA certified. (For example, Dell, Sharp, Ricoh, the U.S. Department of Defense, and many more.) • Three CompTIA Certifications Ranked in the Top 10—In a study by DICE of 17,000 technology professionals, certifications helped command higher salaries at all experience levels. How to Obtain More Information
- 90. • Visit CompTIA online—www.comptia.org to learn more about getting CompTIA certified. • Contact CompTIA—Call 866-835-8020 ext. 5 or emailquestions@comptia.org. • Join the IT Pro community—http://itpro.comptia.org to join the IT community to get relevant career information. • Connect with us— Introduction The CompTIA Network+ certification is a popular certification for those entering the computer-networking field. Although many vendor-specific networking certifications are popular in the industry, the CompTIA Network+ certification is unique in that it is vendor-neutral. The CompTIA Network+ certification often acts as a stepping-stone to more specialized and vendor- specific certifications, such as those offered by Cisco Systems. Notice in your CompTIA Network+ study that the topics are mostly generic, in that they can apply to networking equipment regardless of vendor. However, as you grow in your career, I encourage you to seek specialized training for the equipment you work with on a daily basis. Goals and Methods The goal of this book is twofold. The #1 goal of this book is a simple one: to help you pass the N10-005 version of the CompTIA Network+ exam. To aid you in mastering and understanding the Network+ certification objectives, this book uses the following methods: • Opening topics list: This defines the topics that are covered in the chapter. • Foundation topics: At the heart of a chapter, this section explains the topics from a hands-on and a theory-based standpoint. This includes in-depth descriptions, tables, and figures that build your knowledge so that you can pass the N10-005 exam. The chapters are each broken into multiple sections.
- 91. • Key topics: This indicates important figures, tables, and lists of information that you need to know for the exam. They are sprinkled throughout each chapter and are summarized in table format at the end of each chapter. • Memory tables: These can be found on the DVD within Appendices C and D. Use them to help memorize important information. • Key terms: Key terms without definitions are listed at the end of each chapter. Write down the definition of each term, and check your work against the complete key terms in the Glossary. For current information about the CompTIA Network+ certification exam, you can visithttp://certification.comptia.org/getCertified/certifications/network.aspx. Who Should Read This Book? The CompTIA Network+ exam measures the necessary competencies for an entry-level networking professional with the equivalent knowledge of at least 500 hours of hands-on experience in the lab or field. This book was written for people who have that amount of experience working with computer networks. Average readers will have connected a computer to a network, configured IP addressing on that computer, installed software on that computer, used command-line utilities (for example, the ping command), and used a browser to connect to the Internet. Readers will range from people who are attempting to attain a position in the IT field to people who want to keep their skills sharp or perhaps retain their job because of a company policy that mandates they take the new exams. This book also targets the reader who wants to acquire additional certifications beyond the Network+ certification (for example, the Cisco Certified Network Associate [CCNA] certification and beyond). The book is designed in such a way to offer easy transition to future certification studies. Strategies for Exam Preparation Strategies for exam preparation vary, depending on your existing skills, knowledge, and equipment available. Of course, the ideal exam preparation would include building and configuring a computer network from scratch. Preferably, the network would contain both Microsoft Windows® and UNIX hosts, at least two Ethernet switches, and at least two routers. However, not everyone has access to this equipment, so the next best step you can take is to read the chapters in this book, jotting down notes with key concepts or configurations on a separate notepad. For more visual learners, you might consider the Network+ Video Mentor product by Anthony Sequeira, which is available from Pearson IT Certification, where you get to watch an expert perform multiple configurations. After you read the book, you can download the current exam objectives by submitting a form on the following web
- 92. page:http://certification.comptia.org/Training/testingcenters/examobjectives .aspx If there are any areas shown in the certification exam outline that you still want to study, find those sections in this book and review them. When you feel confident in your skills, attempt the practice exam, which is included on this book’s DVD. As you work through the practice exam, note the areas where you lack confidence and review those concepts or configurations in this book. After you review these areas, work through the practice exam a second time, and rate your skills. Keep in mind that the more you work through the practice exam, the more familiar the questions become, and the practice exam becomes a less accurate judge of your skills. After you work through the practice exam a second time and feel confident with your skills, schedule the real CompTIA Network+ exam (N10-005). The following website provides information about registering for the exam:http://certification.comptia.org/Training/testingcenters.aspx To prevent the information from evaporating out of your mind, you should typically take the exam within a week of when you consider yourself ready to take it. CompTIA Network+ Exam Topics Table I-1 lists general exam topics (objectives) and specific topics under each general topic (subobjectives) for the CompTIA Network+ N10-005 exam. This table also lists the chapter in which each exam topic is covered. Note that some objectives and subobjectives are addressed in multiple chapters. Table I-1 CompTIA Network+ Exam Topics
- 95. How This Book Is Organized Although this book could be read cover-to-cover, it is designed to be flexible and allow you to easily move between chapters and sections of chapters to cover just the material that you need more work with. However, if you do intend to read all the chapters, the order in the book is an excellent sequence to use: • Chapter 1, ―Introducing Computer Networks,‖ introduces the purpose of computer networks and their constituent components. Additionally, networks are categorized by their geography, topology, and resource location. • Chapter 2, ―Dissecting the OSI Model,‖ presents the two network models: the OSI model and the TCP/IP stack. These models categorize various network components from a network cable up to and including an application, such as e-mail. These models are contrasted, and you are given a listing of well-known TCP and UDP port numbers used for specific applications. • Chapter 3, ―Identifying Network Components.‖ A variety of network components are introduced in this chapter. You are given an explanation of various media types, the roles of specific infrastructure components, and the
- 96. features provided by specialized network devices (for example, a firewall or content switch). • Chapter 4, ―Understanding Ethernet.‖ The most widely deployed LAN technology is Ethernet, and this chapter describes the characteristics of Ethernet networks. Topics include media access, collision domains, broadcast domains, and distance/speed limitations for popular Ethernet standards. Additionally, you are introduced to some of the features available on Ethernet switches, such as VLANs, trunks, STP, link aggregation, PoE, port monitoring, and user authentication. • Chapter 5, ―Working with IP Addresses.‖ One of the most challenging concepts for many CompTIA Network+ students is IP subnetting. This chapter demystifies IP subnetting by reviewing the basics of binary numbering, before delving into basic subnetting and then advanced subnetting. Although most of the focus of this chapter is on IP version 4 (IPv4) addressing, the chapter concludes with an introduction to IP version 6 (IPv6). • Chapter 6, ―Routing Traffic.‖ A primary job of a computer network is to route traffic between subnets. This chapter reviews the operation of routing IP traffic and discusses how a router obtains routing information. One way a router can populate its routing table is through the use of dynamic routing protocols, several of which are discussed in this chapter. Many environments (such as a home network connecting to the Internet via a cable modem) use NAT to convert between private IP addresses inside a network and public IP addresses outside a network. This chapter discusses DNAT, SNAT, and PAT. Although the primary focus on this chapter is on unicast routing, the chapter concludes with a discussion of multicast routing. • Chapter 7, ―Introducing Wide-Area Networks.‖ Many corporate networks need to interconnect multiple sites separated by large distances. Connections between such geographically dispersed sites make up a WAN. This chapter discusses three categories of WAN connections and contrasts various WAN connection types, based on supported data rates and media types. Finally, this chapter lists characteristics for multiple WAN technologies. • Chapter 8, ―Connecting Wirelessly.‖ In this increasingly mobile world, wireless technologies are exploding in popularity. This chapter discusses the basic operation of WLANs. Additionally, WLAN design and security considerations are addressed. • Chapter 9, ―Optimizing Network Performance.‖ This chapter explains the importance of high availability for a network and what mechanisms help provide a high level of availability. Network performance optimization strategies are addressed, including a section on QoS. Finally, this chapter allows you to use what you have learned in this and preceding chapters to design a SOHO network.
- 97. • Chapter 10, ―Using Command-Line Utilities.‖ In your daily administration and troubleshooting of computer networks, you need familiarity with various command-line utilities available on the operating systems present in your network. This chapter presents a collection of popular command-line utilities for both Microsoft Windows® and UNIX platforms. • Chapter 11, ―Managing a Network,‖ reviews some of the more common tools used to physically maintain a network. The components of configuration management are also presented. Finally, this chapter discusses some of the network-monitoring tools available to network administrators and what types of information are included in various logs. • Chapter 12, ―Securing a Network.‖ Network security is an issue for most any network, and this chapter covers a variety of network security technologies. You begin by understanding the goals of network security and the types of attacks you must defend against. Then, you review a collection of security best practices. Next, the chapter discusses specific security technologies, including firewalls, VPNs, IDSs, and IPSs. • Chapter 13, ―Troubleshooting Network Issues.‖Troubleshooting network issues in an inherent part of network administration, and this chapter presents a structured approach to troubleshooting various network technologies. Specifically, you learn how to troubleshoot common Layer 2, Layer 3, and wireless network issues. • Chapter 14, ―Final Preparation,‖ reviews the exam-preparation tools available in this book and the enclosed DVD. For example, the enclosed DVD contains a practice exam engine and a collection of ten training videos presented by the author. Finally, a suggested study plan is presented to assist you in preparing for the CompTIA Network+ exam (N10-005). In addition to the 13 main chapters, this book includes tools to help you verify that you are prepared to take the exam. The DVD includes a practice test and memory tables that you can work through to verify your knowledge of the subject matter. The DVD also contains ten training videos that cover some of the most fundamental and misunderstood content in the CompTIA Network+ curriculum, specifically the OSI model and IP addressing. Chapter 1. Introducing Computer Networks After completion of this chapter, you will be able to answer the following questions: • What is the purpose of a network? • What are some examples of network components? • How are networks defined by geography? • How are networks defined by topology? • How are networks defined by resource location?
- 98. What comes to mind when you think of a computer network? Is it the Internet? Is it e-mail? Is it the wireless connection that lets you print to your printer from your laptop? Whatever your current perception of a computer network, this chapter and book, as a whole, helps you gain deep appreciation and understanding of networked computing. Be aware that although we commonly think of computer networks as interconnecting computers, today, computer networks interconnect a variety of devices in addition to just computers. Examples include game consoles, video-surveillance devices, and IP-based telephones. Therefore, throughout this book, you can think of the term computer network as being synonymous with the more generic term network, as these terms will be used interchangeably. In this chapter, the goal is to acquaint you with the purpose of a network and help you categorize a given network based on criteria such as geography, topology, and the location of a network’s resources. An implied goal of this and all other chapters in this book is to prepare you to successfully pass the CompTIA Network+ exam, which is considered to be a cornerstone exam in the information technology (IT) industry. Foundation Topics: Defining a Network It was in the movie A Field of Dreams where they said, ―If you build it, they will come.‖ That phrase most certainly applies to the evolution of network- based services seen in modern-day networks. Computer networks are no longer relegated to allowing a group of computers to access a common set of files stored on a computer designated as a file server. Instead, with the building of high-speed, highly redundant networks, network architects are seeing the wisdom of placing a variety of traffic types on a single network. Examples include voice and video, in addition to data. One could argue that a network is the sum of its parts. So, as you begin your study of networking, you should grasp a basic understanding of fundamental networking components. These components include such entities as a client, server, hub, switch, router, and the media used to interconnect these devices. The Purpose of Networks At its essence, a network’s purpose is to make connections. These connections might be between a PC and a printer or between a laptop and the Internet, as just a couple of examples. However, the true value of a network comes from the traffic flowing over those connections. Consider a sampling of applications that can travel over a network’s connections: • File sharing between two computers • Video chatting between computers located in different parts of the world
- 99. • Surfing the web (for example, to use social media sites, watch streaming video, listen to an Internet radio station, or do research for a school term paper) • Instant messaging (IM) between computers with IM software installed • E-mail • Voice over IP (VoIP), to replace traditional telephony systems A term commonly given to a network transporting multiple types of traffic (for example, voice, video, and data) is a converged network. A converged network might offer significant cost savings to organizations that previously supported separate network infrastructures for voice, data, and video traffic. This convergence can also potentially reduce staffing costs, because only a single network needs to be maintained, rather than separate networks for separate traffic types. Overview of Network Components Designing, installing, administering, and troubleshooting a network requires the ability to recognize various network components and their functions. Although this is the focus of Chapter 3, ―Identifying Network Components,‖ before we can proceed much further, we need a basic working knowledge of how individual components come together to form a functioning network. The components to consider for now are client, server, hub, switch, router, media, and wide-area network (WAN) link. As a reference for this discussion, consider Figure 1-1. Figure 1-1 Sample Computer Network The following list describes the network components depicted in Figure 1- 1 and the functions they serve: • Client: The term client defines the device an end user uses to access a network. This device might be a workstation, laptop, smartphone with wireless capabilities, or a variety of other end-user terminal devices.
- 100. • Server: A server, as the name suggests, serves up resources to a network. These resources might include e-mail access as provided by an e-mail server, web pages as provided by a web server, or files available on a file server. • Hub: A hub is an older technology that interconnects network components, such as clients and servers. Hubs vary in their number of available ports. However, for scalability, hubs can be interconnected, up to a point. If too many hubs are chained together, network errors can result. As discussed further in Chapter 3, a hub does not perform any inspection of the traffic it passes. Rather, a hub simply receives traffic in a port (that is, a receptacle to which a network cable connects) and repeats that traffic out all of the other ports. • Switch: Like a hub, a switch interconnects network components, and they are available with a variety of port densities. However, unlike a hub, a switch does not simply take traffic in on one port and blast that traffic out all other ports. Rather, a switch learns which devices reside off of which ports. As a result, when traffic comes in a switch port, the switch interrogates the traffic to see where it is destined. Then, based on what the switch has learned, the switch forwards the traffic out of the appropriate port, and not out all of the other ports. This dramatically cuts down on the volume of traffic coursing through your network. A switch is considered a Layer 2 device, which means that it makes its forwarding decisions based on addresses that are physically burned into a network interface card (NIC) installed in ahost (that is, any device that transmits or receives traffic on a network). This burned-in address is a Media Access Control (MAC) address. • Router: As discussed in Chapter 3, a router is considered to be aLayer 3 device, which means that it makes its forwarding decisions based on logical network addresses. Most modern networks useInternet Protocol (IP) addressing. Therefore, most routers know what logical IP networks reside off of which router interfaces. Then, when traffic comes into a router, the router examines the destination IP address of the traffic and, based on the router’s database of networks (that is, the routing table), the router intelligently forwards the traffic out the appropriate interface. • Media: The previously mentioned devices need to be interconnected via some sort of media. This media could be copper cabling. It could be a fiber- optic cable. Media might not even be a cable, as is the case with wireless networks, where radio waves travel through the media of air.Chapter 3 expands on this discussion of media. For now, realize that media varies in its cost, bandwidth capacity, and distance limitation. For example, although fiber-optic cabling is more expensive than unshielded twisted-pair cabling, it can typically carry traffic over longer distances and has a greater bandwidth capacity (that is, the capacity to carry a higher data rate).
- 101. • WAN link: Today, most networks connect to one or more other networks. For example, if your company has two locations, and those two locations are interconnected (perhaps via a Frame Relay or Multiprotocol Label Switching [MPLS] network), the link that interconnects those networks is typically referred to as a wide-area network (WAN) link. WANs, and technologies supporting WANs, are covered in Chapter 7, ―Introducing Wide-Area Networks.‖ Networks Defined by Geography As you might be sensing at this point, not all networks look the same. They vary in numerous ways. One criterion by which we can classify networks is how geographically dispersed the networks components are. For example, a network might interconnect devices within an office, or a network might interconnect a database at a corporate headquarters location with a remote sales office located on the opposite side of the globe. Based on the geographical dispersion of network components, networks can be classified into various categories, including the following: • Local-area network (LAN) • Wide-area network (WAN) • Campus-area network (CAN) • Metropolitan-area network (MAN) • Personal-area network (PAN) The following sections describe these different classifications of networks in more detail. LAN A LAN interconnects network components within a local region (for example, within a building). Examples of common LAN technologies you’re likely to encounter include Ethernet (that is, IEEE 802.3) and wireless networks (that is, IEEE 802.11). Figure 1-2 illustrates an example of a LAN. Figure 1-2 Sample LAN Topology
- 102. Note IEEE stands for the Institute of Electrical and Electronics Engineers, and it is an internationally recognized standards body. WAN A WAN interconnects network components that are geographically separated. For example, a corporate headquarters might have multiple WAN connections to remote office sites. Multiprotocol Label Switching (MPLS), Asynchronous Transfer Mode (ATM), and Frame Relay are examples of WAN technologies.Figure 1-3 depicts a simple WAN topology, which interconnects two geographically dispersed locations. Figure 1-3 Sample WAN Topology Other Categories of Networks Although LANs and WANs are the most common terms used to categorize computer networks based on geography, other categories include campus-area network (CAN), metropolitan-area network (MAN), and personal-area network (PAN). CAN
- 103. Years ago, I was a network manager for a university. The university covered several square miles and had several dozen buildings. Within many of these buildings was a LAN. However, those building-centric LANs were interconnected. By interconnecting these LANs, another network type was created, a CAN. Besides an actual university campus, a CAN might also be found in an industrial park or business park. MAN More widespread than a CAN and less widespread than a WAN, a MAN interconnects locations scattered throughout a metropolitan area. Imagine, for example, that a business in Chicago had a location near O’Hare Airport, another location near the Navy Pier, and another location in the Sears Tower. If a service provider could interconnect those locations using a high-speed network, such as a 10-Gbps (that is, 10 billion bits per second) network, the interconnection of those locations would constitute a MAN. One example of a MAN technology is Metro Ethernet. PAN A PAN is a network whose scale is even smaller than a LAN. As an example, a connection between a PC and a digital camera via a universal serial bus (USB) cable could be considered a PAN. Another example is a PC connected to an external hard drive via a FireWire connection. A PAN, however, is not necessarily a wired connection. A Bluetooth connection between your cell phone and your car’s audio system is considered a wireless PAN (WPAN). The main distinction of a PAN, however, is that its range is typically limited to just a few meters. Networks Defined by Topology In addition to classifying networks based on the geographical placement of their components, another approach to classifying a network is to use the network’s topology. Looks can be deceiving, however. You need to be able to distinguish between a physical topology and a logical topology. Physical Versus Logical Topology Just because a network appears to be a star topology (that is, where the network components all connect back to a centralized device, such as a switch), the traffic might be flowing in a circular pattern through all the network components attached to the centralized device. The actual traffic flow determines the logical topology, while how components are physically interconnected determines thephysical topology. As an example, consider Figure 1-4. The figure shows a collection of computers connected to a Token Ring Media Access Unit (MAU). From a quick inspection ofFigure 1-4, you can conclude that the devices are physically
- 104. connected in a star topology, where the connected devices radiate out from a centralized aggregation point (that is, the MAU in this example). Figure 1-4 Physical Star Topology Next, contrast the physical topology in Figure 1-4 with the logical topology illustrated in Figure 1-5. Although the computers physically connect to a centralized MAU, when you examine the flow of traffic through (or in this case, around) the network, you see that the traffic flow actually loops round- and-round the network. The traffic flow dictates how to classify a network’s logical topology. In this instance, the logical topology is a ring topology, because the traffic circulates around the network as if circulating around a ring. Figure 1-5 Logical Ring Topology
- 105. Although Token Ring, as used in this example, is rarely seen in modern networks, it illustrates how a network’s physical and logical topologies can be quite different. Bus Topology A bus topology, as depicted in Figure 1-6, typically uses a cable running through the area requiring connectivity. Devices that need to connect to the network then tap into this nearby cable. Early Ethernet networks commonly relied on bus topologies. Figure 1-6 Bus Topology A network tap might be in the form of a T connector (commonly used in older 10BASE2 networks) or a vampire tap (commonly used in older 10BASE5 networks). Figure 1-7 shows an example of a T connector. Figure 1-7 T Connector
- 106. Note The Ethernet standards mentioned here (that is, 10BASE2 and 10BASE5), in addition to many other Ethernet standards, are discussed in detail in Chapter 4, ―Understanding Ethernet.‖ A bus and all devices connected to that bus make up a network segment. As discussed in Chapter 4, a single network segment is a single collision domain, which means that all devices connected to the bus might try to gain access to the bus at the same time, resulting in an error condition known as a collision. Table 1-1 identifies some of the primary characteristics, benefits, and drawbacks of a bus topology. Table 1-1 Characteristics, Benefits, and Drawbacks of a Bus Topology
- 107. Ring Topology Figure 1-8 offers an example of a ring topology, where traffic flows in a circular fashion around a closed network loop (that is, a ring). Typically, a ring topology sends data, in a single direction, to each connected device in turn, until the intended destination receives the data. Token Ring networks typically relied on a ring topology, although the ring might have been the logical topology, while physically, the topology was a star topology. Figure 1-8 Ring Topology
- 108. Token Ring, however, was not the only popular ring-based topology popular in networks back in the 1990s. Fiber Distributed Data Interface (FDDI) was another variant of a ring-based topology. Most FDDI networks (which, as the name suggests, have fiber optics as the media) used not just one ring, but two. These two rings sent data in opposite directions, resulting in counter-rotating rings. One benefit of counter-rotating rings was that if a fiber broke, the stations on each side of the break could interconnect their two rings, resulting in a single ring capable of reaching all stations on the ring. Because a ring topology allows devices on the ring to take turns transmitting on the ring, contention for media access was not a problem, as it was for a bus topology. If a network had a single ring, however, the ring became a single point of failure. If the ring were broken at any point, data would stop flowing. Table 1-2identifies some of the primary characteristics, benefits, and drawbacks of a ring topology. Table 1-2 Characteristics, Benefits, and Drawbacks of a Ring Topology
- 109. Star Topology Figure 1-9 shows a sample star topology with a hub at the center of the topology and a collection of clients individually connected to the hub. Notice that a star topology has a central point from which all attached devices radiate. In LANs, that centralized device was typically a hub back in the early 1990s. Modern networks, however, usually have a switch located at the center of the star. Figure 1-9 Star Topology
- 110. Note Chapter 3 discusses UTP and other types of cabling. The star topology is the most popular physical LAN topology in use today, with an Ethernet switch at the center of the star and unshielded twisted-pair cable (UTP) used to connect from the switch ports to clients. Table 1-3 identifies some of the primary characteristics, benefits, and drawbacks of a star topology. Table 1-3 Characteristics, Benefits, and Drawbacks of a Star Topology Hub-and-Spoke Topology When interconnecting multiple sites (for example, multiple corporate locations) via WAN links, a hub-and-spoke topology has a WAN link from each remote site (that is, a spoke site) to the main site (that is, the hub site). This approach, an example of which is shown in Figure 1-10, is similar to the star topology used in LANs. Figure 1-10 Hub-and-Spoke Topology
- 111. With WAN links, a service provider is paid a recurring fee for each link. Therefore, a hub-and-spoke topology helps minimize WAN expenses by not directly connecting any two spoke locations. If two spoke locations need to communicate between themselves, their communication is sent via the hub location. Table 1-4 contrasts the benefits and drawbacks of a hub-and-spoke WAN topology. Table 1-4 Characteristics, Benefits, and Drawbacks of a Hub-and-Spoke WAN Topology
- 112. Full-Mesh Topology Although a hub-and-spoke WAN topology lacked redundancy and suffered from suboptimal routes, a full-mesh topology, as shown in Figure 1-11, directly connects every site to every other site. Figure 1-11 Full-Mesh Topology Because each site connects directly to every other site, an optimal path can be selected, as opposed to relaying traffic via another site. Also, a full-mesh topology is highly fault tolerant. By inspecting Figure 1-11, you can see that multiple links in the topology could be lost, and every site might still be able to connect to every other site. Table 1-5 summarizes the characteristics of a full- mesh topology. Table 1-5 Characteristics, Benefits, and Drawbacks of a Full-Mesh WAN Topology
- 113. Partial-Mesh Topology A partial-mesh WAN topology, as depicted in Figure 1-12, is a hybrid of the previously described hub-and-spoke topology and full-mesh topology. Specifically, a partial-mesh topology can be designed to provide an optimal route between selected sites, while avoiding the expense of interconnecting every site to every other site. Figure 1-12 Partial-Mesh Topology
- 114. When designing a partial-mesh topology, a network designer must consider network traffic patterns and strategically add links interconnecting sites that have higher volumes of traffic between themselves. Table 1-6 highlights the characteristics, benefits, and drawbacks of a partial-mesh topology. Table 1-6 Characteristics, Benefits, and Drawbacks of a Partial-Mesh Topology Networks Defined by Resource Location Yet another way to categorize networks is based on where network resources reside. An example of a client-server network is a collection of PCs all sharing files located on a centralized server. However, if those PCs had their operating system (OS) (for example, Microsoft Windows 7 or Mac OS X) configured for
- 115. file sharing, they could share files from one another’s hard drives. Such an arrangement would be referred to as a peer-to-peer network, because the peers (that is, the PCs in this example) make resources available to other peers. The following sections describe client-server and peer-to-peer networks in more detail. Client-Server Networks Figure 1-13 illustrates an example of a client-server network, where a dedicated file server provides shared access to files, and a networked printer is available as a resource to the network’s clients. Client-server networks are commonly used by businesses. Because resources are located on one or more servers, administration is simpler than trying to administer network resources on multiple peer devices. Figure 1-13 Client-Server Network Example Performance of a client-server network can be better than that of a peer-to- peer network, because resources can be located on dedicated servers, rather than on a PC running a variety of end-user applications. Backups can be simplified, since fewer locations must be backed up. However, client-server networks come with the extra expense of dedicated server resources. Table 1- 7 contrasts the benefits and drawbacks of client-server networks. Table 1-7 Characteristics, Benefits, and Drawbacks of a Client-Server Network
- 116. Note A server in a client-server network could be a computer running anetwork operating system (NOS), such as Novell NetWare or a variety of Microsoft Windows Server OSs. Alternately, a server might be a host making its file system available to remote clients via the Network File System (NFS) service, which was originally developed by Sun Microsystems. Note A variant of the traditional server in a client-server network, where the server provides shared file access, is network-attached storage (NAS). A NAS device is a mass storage device that attaches directly to a network. Rather than running an advanced NOS, a NAS device typically makes files available to network clients via a service such as NFS. Peer-to-Peer Networks Peer-to-peer networks allow interconnected devices (for example, PCs) to share their resources with one another. Those resources could be, for example, files or printers. As an example of a peer-to-peer network, consider Figure 1- 14, where each of the peers can share files on their own hard drives, and one of the peers has a directly attached printer that can be shared with the other peers in the network. Figure 1-14 Peer-to-Peer Network Example
- 117. Peer-to-peer networks are commonly seen in smaller businesses and in homes. The popularity of these peer-to-peer networks is fueled in part by client operating systems which support file and print sharing. Scalability for peer-to-peer networks is a concern, however. Specifically, as the number of devices (that is, peers) increases, the administration burden increases. For example, a network administrator might have to manage file permissions on multiple devices, as opposed to a single server. Consider the characteristics of peer-to-peer networks as presented in Table 1-8. Table 1-8 Characteristics, Benefits, and Drawbacks of a Peer-to-Peer Network
- 118. Note Some networks have characteristics of both peer-to-peer and client-server networks. For example, PCs in a company might all point to a centralized server for accessing a shared database in a client-server topology. However, these PCs might simultaneously share files and printers between one another in a peer-to-peer topology. Such a network, which has a mixture of client- server and peer-to-peer characteristics, is called a hybrid network. Summary The main topics covered in this chapter are the following: • You were introduced to various network components, including client, server, hub, switch, router, media, and WAN link. • One way to classify networks is by their geographical dispersion. Specifically, these network types were identified: LAN, WAN, CAN, MAN, and PAN. • Another approach to classifying networks is based on a network’s topology. Examples of network types, based on topology, include bus, ring, star, partial mesh, full mesh, and hub-and-spoke. • This chapter contrasted client-server and peer-to-peer networks. Exam Preparation Tasks Review All the Key Topics Review the most important topics from inside the chapter, noted with the Key Topic icon in the outer margin of the page. Table 1-9 lists these key topics and the page numbers where each is found. Table 1-9 Key Topics for Chapter 1
- 119. Complete Tables and Lists from Memory Print a copy of Appendix C, ―Memory Tables‖ (found on the DVD), or at least the section for this chapter, and complete as much of the tables as possible from memory. Appendix D, ―Memory Tables Answer Key,‖ also on the DVD, includes the completed tables and lists so you can check your work. Define Key Terms Define the following key terms from this chapter, and check your answers in the Glossary: client, server, hub, switch, router, media, WAN link, local-area network (LAN), wide-area network (WAN), campus-area network (CAN), metropolitan-area network (MAN), personal-area network (PAN), logical topology, physical topology, bus topology, ring topology, star topology, hub-and-spoke topology, full-mesh topology, partial-mesh topology, client-server network, peer-to-peer network Review Questions The answers to these review questions appear in Appendix A, ―Answers to Review Questions.‖ 1. Which of the following is a device directly used by an end user to access a network? a. Server b. LAN c. Client d. Router 2. Which device makes traffic-forwarding decisions based on MAC addresses? a. Hub
- 120. b. Router c. Switch d. Multiplexer 3. A company has various locations in a city interconnected using Metro Ethernet connections. This is an example of what type of network? a. WAN b. CAN c. PAN d. MAN 4. A network formed by interconnecting a PC to a digital camera via a USB cable is considered what type of network? a. WAN b. CAN c. PAN d. MAN 5. Which of the following LAN topologies requires the most cabling? a. Bus b. Ring c. Star d. WLAN 6. Which of the following topologies offers the highest level of redundancy? a. Full mesh b. Hub and spoke c. Bus d. Partial mesh 7. How many WAN links are required to create a full mesh of connections between five remote sites? a. 5 b. 10 c. 15 d. 20 8. Identify two advantages of a hub-and-spoke WAN topology as compared to a full-mesh WAN topology. (Choose two.) a. Lower cost b. Optimal routes c. More scalable d. More redundancy 9. Which type of network is based on network clients sharing resources with one another? a. Client-server b. Client-peer c. Peer-to-peer
- 121. d. Peer-to-server 10. Which of the following is an advantage of a peer-to-peer network, as compared with a client-server network? a. More scalable b. Less expensive c. Better performance d. Simplified administration Chapter 2. Dissecting the OSI Model After completion of this chapter, you will be able to answer the following questions: • What is the purpose of a network model? • What are the layers of the OSI model? • What are the characteristics of each layer of the OSI model? • How does the TCP/IP stack compare to the OSI model? • What are the well-known TCP and/or UDP port numbers for a given collection of common applications? Way back in 1977, the International Organization for Standardization (ISO) developed a subcommittee to focus on the interoperability of multivendor communications systems. What sprang from this subcommittee was the Open Systems Interconnection (OSI) reference model (commonly referred to as the OSI model or the OSI stack). With this model, you can take just about any networking technology and categorize that technology as residing at one or more of the seven layers of the model. This chapter defines those seven layers and provides examples of what you might find at each layer. Finally, this chapter contrasts the OSI model with another model (the TCP/IP stack, also known as the Department of Defense [DoD]model), which focuses on Internet Protocol (IP) communications. Foundation Topics: The Purpose of Reference Models Throughout your networking career, and throughout this book, you will encounter various protocols and devices that play a role in your network. To better understand how a particular technology fits in, however, it helps to have a common point of reference against which various technologies from various vendors can be compared. One of the most common ways of categorizing the function of a network technology is to state at what layer (or layers) of the OSI model that technology operates. Based on how that technology performs a certain function at a certain layer of the OSI model, you can better determine if one device is going to be able to communicate with another device, which might or
- 122. might not be using a similar technology at that layer of the OSI reference model. For example, when your laptop connects to a web server on the Internet, your laptop has been assigned an IP address. Similarly, the web server to which you are communicating has an IP address. As you see in this chapter, an IP address lives at Layer 3 (the network layer) of the OSI model. Because both your laptop and the web server use a common protocol (that is, IP) at Layer 3, they can communicate with one another. Personally, I’ve been in the computer-networking industry since 1989, and I have had the OSI model explained in many classes I’ve attended and books I’ve read. From this, I’ve taken away a collection of metaphors to help describe the operation of the different layers of the OSI model. Some of the metaphors involve sending a letter from one location to another or placing a message in a series of envelopes. However, my favorite (and the most accurate) way to describe the OSI model is to simply think of it as being analogous to a bookshelf, such as the one shown in Figure 2-1. Figure 2-1 A Bookshelf Is Analogous to the OSI Model If you were to look at a bookshelf in my home, you’d see that I organized different types of books on different shelves. One shelf contains my collection of Star Wars books, another shelf contains the books I wrote for Cisco Press, another shelf contains my audio books, and so on. I grouped similar books together on a shelf, just as the OSI model groups similar protocols and functions together in a layer.
- 123. A common pitfall my students and readers encounter when studying the OSI model is to try to neatly fit all the devices and protocols in their network into one of the OSI model’s seven layers. However, not every technology is a perfect fit into these layers. In fact, some networks might not have any technologies operating at one or more of these layers. This reminds me of my favorite statement regarding the OSI model. It comes from Rich Seifert’s book The Switch Book. In that book, Rich reminds us that the OSI model is a reference model, not a reverence model. That is, there is no cosmic law stating that all technologies must cleanly plug into the model. So, as you discover the characteristics of the OSI model layers throughout this chapter, remember that these layers are like shelves for organizing similar protocols and functions, not immutable laws. The OSI Model As previously stated, the OSI model is comprised of seven layers: • Layer 1: The physical layer • Layer 2: The data link layer • Layer 3: The network layer • Layer 4: The transport layer • Layer 5: The session layer • Layer 6: The presentation layer • Layer 7: The application layer Graphically, these layers are usually depicted with Layer 1 at the bottom of the stack, as shown in Figure 2-2. Figure 2-2 OSI ―Stack‖ Various mnemonics are available to help memorize these layers in their proper order. A top-down (that is, starting at the top of the stack with Layer 7 and working your way down to Layer 1) acrostic is All People Seem To Need Data Processing. As a couple of examples, using this acrostic, the A in All
- 124. reminds us of the A in Application, and the P in People reminds us of the P in Presentation. At the physical layer, binary expressions (that is, a series of 1s and 0s) represent data. A binary expression is made up of bits, where a bit is a single 1 or a single 0. At upper layers, however, bits are grouped together, into what is known as aprotocol data unit (PDU) or a data service unit. The term packet is used fairly generically to refer to these PDUs. However, PDUs might have an additional name, depending on their OSI layer. Figure 2- 3illustrates these PDU names. A common memory aid for these PDUs is the acrostic Some People Fear Birthdays, where the S in Some reminds us of the S inSegments. The P in People reminds us of the P in Packets, and the F in Fear reflects the F in Frames. Finally, the B in Birthdays reminds us of the B in Bits. Figure 2-3 PDU Names Layer 1: The Physical Layer The physical layer, as shown in Figure 2-4, is concerned with the transmission of data on the network. Figure 2-4 Layer 1: The Physical Layer
- 125. As a few examples, the physical layer defines • How bits are represented on the medium: Data on a computer network is represented as a binary expression. Chapter 5, ―Working with IP Addresses,‖ discusses binary in much more detail. Electrical voltage (on copper wiring) or light (carried via fiber-optic cabling) can represent these 1s and 0s. For example, the presence or the absence of voltage on a wire can represent a binary 1 or a binary 0, respectively, as illustrated in Figure 2-5. Similarly, the presence or absence of light on a fiber-optic cable can represent a 1 or 0 in binary. This type of approach is called current state modulation. Figure 2-5 Current State Modulation An alternate approach to representing binary data is state transition modulation, as shown in Figure 2-6, where the transition between voltages or the presence of light indicates a binary value. Figure 2-6 Transition Modulation
- 126. Note Other modulation types you might be familiar with from radio include amplitude modulation (AM) and frequency modulation (FM). AM uses a variation in a waveform’s amplitude (that is, signal strength) to represent the original signal. However, FM uses a variation in frequency to represent the original signal. • Wiring standards for connectors and jacks: Several standards for network connectors are addressed in Chapter 3, ―Identifying Network Components.‖ As an example, however, the TIA/EIA-568-B standard describes how an RJ-45 connector should be wired for use on a 100BASE-TX Ethernet network, as shown in Figure 2-7. Figure 2-7 TIA/EIA-568-B Wiring Standard for an RJ-45 Connector • Physical topology: Layer 1 devices view a network as a physical topology (as opposed to a logical topology). Examples of a physical topology include bus, ring, and star topologies, as described in Chapter 1, ―Introducing Computer Networks.‖ • Synchronizing bits: For two networked devices to successfully communicate at the physical layer, they must agree on when one bit stops and another bit starts. Specifically, what is needed is a method to synchronize the bits. Two basic approaches to bit synchronization include asynchronous and synchronous synchronization: • Asynchronous: With this approach, a sender indicates that it’s about to start transmitting by sending a start bit to the receiver. When the receiver sees
- 127. this, it starts its own internal clock to measure the subsequent bits. After the sender transmits its data, it sends a stop bit to indicate that is has finished its transmission. • Synchronous: This approach synchronizes the internal clocks of both the sender and receiver to ensure that they agree on when bits begin and end. A common approach to make this synchronization happen is to use an external clock (for example, a clock provided by a service provider), which is referenced by both the sender and receiver. • Bandwidth usage: The two fundamental approaches to bandwidth usage on a network are broadband and baseband: • Broadband: Broadband technologies divide the bandwidth available on a medium (for example, copper or fiber-optic cabling) into different channels. Different communication streams are then transmitted over the various channels. As an example, considerFrequency-Division Multiplexing (FDM) used by a cable modem. Specifically, a cable modem uses certain ranges of frequencies on the cable coming into your home from the local cable company to carry incoming data, another range of frequencies for outgoing data, and several other frequency ranges for various TV stations. • Baseband: Baseband technologies, in contrast, use all the available frequencies on a medium to transmit data. Ethernet is an example of a networking technology that uses baseband. • Multiplexing strategy: Multiplexing allows multiple communications sessions to share the same physical medium. Cable TV, as previously mentioned, allows you to receive multiple channels over a single physical medium (for example, a coaxial cable plugged into the back of your television). Here are some of the more common approaches to multiplexing: • Time-division multiplexing (TDM): TDM supports different communication sessions (for example, different telephone conversations in a telephony network) on the same physical medium by causing the sessions to take turns. For a brief period of time, defined as a time slotdata from the first session will be sent, followed by data from the second session. This continues until all sessions have had a turn, and the process repeats itself. • Statistical time-division multiplexing (StatTDM): A downside to TDM is that each communication session receives its own time slot, even if one of the sessions does not have any data to transmit at the moment. To make a more efficient use of available bandwidth, StatTDM dynamically assigns time slots to communications sessions on an as-needed basis. • Frequency-division multiplexing (FDM): FDM divides a medium’s frequency range into channels, and different communication sessions transmit their data over different channels. As previously described, this approach to bandwidth usage is called broadband.
- 128. Examples of devices defined by physical layer standards include hubs, wireless access points, and network cabling. Note A hub can interconnect PCs in a LAN. However, it is considered to be a physical layer device, because a hub takes bits coming in on one port and retransmits those bits out all other hub ports. At no point does the hub interrogate any addressing information in the data. Layer 2: The Data Link Layer The data link layer, as shown in Figure 2-8, is concerned with packaging data into frames and transmitting those frames on the network, performing error detection/correction, uniquely identifying network devices with an address, and handling flow control. These processes are collectively referred to as data link control (DLC). Figure 2-8 Layer 2: The Data Link Layer In fact, the data link layer is unique from the other layers in that it has two sublayers of its own: MAC and LLC. Media Access Control Characteristics of the Media Access Control (MAC) sublayer include the following: • Physical addressing: A common example of a Layer 2 address is a MAC address, which is a 48-bit address assigned to a device’s network interface card (NIC). The address is commonly written in hexadecimal notation (for example, 58:55:ca:eb:27:83). The first 24 bits of the 48-bit address are collectively referred to as the vendor code. Vendors of networking equipment are assigned one or more unique vendor codes. You can use the list of vendor
- 129. codes athttp://standards.ieee.org/develop/regauth/oui/oui.txt to determine the manufacturer of a networking device, based on the first half of the device’s MAC address. Because each vendor is responsible for using unique values in the last 24 bits of a MAC address, and because each vendor has a unique vendor code, no two MAC addresses in the world should have the same value. • Logical topology: Layer 2 devices view a network as a logical topology. Examples of a logical topology include bus and ring topologies, as described in Chapter 1. • Method of transmitting on the media: With several devices connected to a network, there needs to be some strategy for determining when a device is allowed to transmit on the media. Otherwise, multiple devices might transmit at the same time, and interfere with one another’s transmissions. Logical Link Control Characteristics of the Logical Link Control (LLC) sublayer include the following: • Connection services: When a device on a network receives a message from another device on the network, that recipient device can provide feedback to the sender in the form of an acknowledgment message. The two main functions provided by these acknowledgment messages are as follows: • Flow control: Limits the amount of data a sender can send at one time; this prevents the receiver from being overwhelmed with too much information. • Error control: Allows the recipient of data to let the sender know if the expected data frame was not received or if it was received, but is corrupted. The recipient determines if the data frame is corrupted by mathematically calculating a checksum of the data received. If the calculated checksum does not match the checksum received with the data frame, the recipient of the data draws the conclusion that the data frame is corrupted and can then notify the sender via an acknowledgment message. • Synchronizing transmissions: Senders and receivers of data frames need to coordinate when a data frame is being transmitted and should be received. Three methods of performing this synchronization are as follows: • Isochronous: With isochronous transmission, network devices look to a common device in the network as a clock source, which creates fixed-length time slots. Network devices can determine how much free space, if any, is available within a time slot and insert data into an available time slot. A time slot can accommodate more than one data frame. Isochronous transmission does not need to provide clocking at the beginning of a data string (as does synchronous transmission) or for every data frame (as does asynchronous transmission). As a result, isochronous transmission uses little overhead when compared to asynchronous or synchronous transmission methods.
- 130. • Asynchronous: With asynchronous transmission, network devices reference their own internal clocks, and network devices do not need to synchronize their clocks. Instead, the sender places a start bit at the beginning of each data frame and a stop bit at the end of each data frame. These start and stop bits tell the receiver when to monitor the medium for the presence of bits. An additional bit, called the parity bit, might also be added to the end of each byte in a frame to detect an error in the frame. For example, if even parity error detection (as opposed to odd parity error detection) is used, the parity bit (with a value of either 0 or 1) would be added to the end of a byte, causing the total number of 1s in the data frame to be an even number. If the receiver of a byte is configured for even parity error detection and receives a byte where the total number of bits (including the parity bit) is even, the receiver can conclude that the byte was not corrupted during transmission. Note Using a parity bit to detect errors might not be effective if a byte has more than one error (that is, more than one bit that has been changed from its original value). • Synchronous: With synchronous transmission, two network devices that want to communicate between themselves must agree on a clocking method to indicate the beginning and ending of data frames. One approach to providing this clocking is to use a separate communications channel over which a clock signal is sent. Another approach relies on specific bit combinations or control characters to indicate the beginning of a frame or a byte of data. Like asynchronous transmissions, synchronous transmissions can perform error detection. However, rather than using parity bits, synchronous communication runs a mathematical algorithm on the data to create a cyclic redundancy check (CRC). If both the sender and receiver calculate the same CRC value for the same chunk of data, the receiver can conclude that the data was not corrupted during transmission. Examples of devices defined by data link layer standards include switches, bridges, and network interface cards (NIC). Note NICs are not entirely defined at the data link layer, because they are partially based on physical layer standards, such as a NIC’s network connector. Layer 3: The Network Layer The network layer, as shown in Figure 2-9, is primarily concerned with forwarding data based on logical addresses.
- 131. Figure 2-9 Layer 3: The Network Layer Although many network administrators immediately think of routing and IP addressing when they hear about the network layer, this layer is actually responsible for a variety of tasks: • Logical addressing: Although the data link layer uses physical addresses to make forwarding decisions, the network layer uses logical addressing to make forwarding decisions. A variety of routed protocols (for example, AppleTalk and IPX) have their own logical addressing schemes, but by far, the most widely deployed routed protocol is Internet Protocol (IP). IP addressing is discussed in detail in Chapter 5, ―Working with IP Addresses.‖ • Switching: The term switching is often associated with Layer 2 technologies; however, the concept of switching also exists at Layer 3. Switching, at its essence, is making decisions about how data should be forwarded. At Layer 3, three common switching techniques exist: • Packet switching: With packet switching, a data stream is divided into packets. Each packet has a Layer 3 header, which includes a source and destination Layer 3 address. Another term for packet switching is routing, which is discussed in more detail in Chapter 6, ―Routing Traffic.‖ • Circuit switching: Circuit switching dynamically brings up a dedicated communication link between two parties in order for those parties to communicate. As a simple example of circuit switching, think of making a phone call from your home to a business. Assuming you have a traditional landline servicing your phone, the telephone company’s switching equipment interconnects your home phone with the phone system of the business you’re calling. This interconnection (that is, circuit) only exists for the duration of the phone call. • Message switching: Unlike packet switching and circuit switching technologies, message switching is usually not well-suited for real-time applications, because of the delay involved. Specifically, with message
- 132. switching, a data stream is divided into messages. Each message is tagged with a destination address, and the messages travel from one network device to another network device on the way to their destination. Because these devices might briefly store the messages before forwarding them, a network using message switching is sometimes called a store-and-forward network. Metaphorically, you could visualize message switching like routing an e-mail message, where the e-mail message might be briefly stored on an e-mail server before being forwarded to the recipient. • Route discovery and selection: Because Layer 3 devices make forwarding decisions based on logical network addresses, a Layer 3 device might need to know how to reach various network addresses. For example, a common Layer 3 device is a router. A router can maintain a routing table indicating how to forward a packet based on the packet’s destination network address. A router can have its routing table populated via manual configuration (that is, by entering static routes), via a dynamic routing protocol (for example, RIP, OSPF, or EIGRP), or simply by the fact that the router is directly connected to certain networks. Note Routing protocols are discussed in Chapter 6. • Connection services: Just as the data link layer provided connection services for flow control and error control, connection services also exist at the network layer. Connection services at the network layer can improve the communication reliability, in the event that the data link’s LLC sublayer is not performing connection services. The following functions are performed by connection services at the network layer: • Flow control (also known as congestion control): Helps prevent a sender from sending data more rapidly that the receiver is capable is receiving the data. • Packet reordering: Allows packets to be placed in the appropriate sequence as they are sent to the receiver. This might be necessary, because some networks support load-balancing, where multiple links are used to send packets between two devices. Because multiple links are used, packets might arrive out of order. Examples of devices found at the network layer include routers and multilayer switches. The most common Layer 3 protocol in use today, and the protocol on which the Internet is based, is IP. A less popular Layer 3 protocol is Novell’s Internetwork Packet Exchange (IPX), which has its own format for Layer 3 addressing. Although
- 133. IPX is a Novell-developed protocol, most modern Novell networks use IP as their Layer 3 protocol. Note Routers and multilayer switches are discussed in Chapter 3. Layer 4: The Transport Layer The transport layer, as shown in Figure 2-10, acts as a dividing line between the upper layers and lower layers of the OSI model. Specifically, messages are taken from upper layers (Layers 5–7) and are encapsulated into segments for transmission to the lower layers (Layers 1–3). Similarly, data streams coming from lower layers are decapsulated and sent to Layer 5 (the session layer), or some other upper layer, depending on the protocol. Figure 2-10 Layer 4: The Transport Layer Two common transport layer protocols include Transmission Control Protocol(TCP) and User Datagram Protocol (UDP): • Transmission Control Protocol (TCP): A connection-oriented transport protocol. Connection-oriented transport protocols provide reliable transport, in that if a segment is dropped, the sender can detect that drop and retransmit that dropped segment. Specifically, a receiver acknowledges segments that it receives. Based on those acknowledgments, a sender can determine which segments were successfully received and which segments need to be transmitted again. • User Datagram Protocol (UDP): A connectionless transport protocol. Connectionless transport protocols provide unreliable transport, in that if a segment is dropped, the sender is unaware of the drop, and no retransmission occurs. A less popular Layer 4 protocol is Novell’s Sequenced Packet Exchange (SPX). Similar to the TCP/IP stack of protocols, Novell’s solution (much more
- 134. popular in the mid 1990s) was the IPX/SPX stack of protocols. However, most modern Novell networks rely on TCP/IP rather than IPX/SPX. Note Microsoft introduced its own implementation of Novell’s IPX/SPX, which was named NWLink IPX/SPX. Just as Layer 2 and Layer 3 each offer flow control services, flow control services also exist at Layer 4. Two common flow control approaches at Layer 4 are as follows: • Windowing: TCP communication uses windowing, in that one or more segments are sent at one time, and a receiver can acknowledge the receipt of all the segments in a window with a single acknowledgment. In some cases, as illustrated in Figure 2-11, TCP uses a sliding window, where the window size begins with one segment. If there is a successful acknowledgment of that one segment (that is, the receiver sends an acknowledgment asking for the next segment), the window size doubles to two segments. Upon successful receipt of those two segments, the next window contains four segments. This exponential increase in window size continues until the receiver does not acknowledge successful receipt of all segments within a certain time period (known as the round trip time [RTT], which is sometimes called real transfer time), or until a configured maximum window size is reached. Figure 2-11 TCP Sliding Window
- 135. • Buffering: With buffering, a device (for example, a router) allocates a chunk of memory (sometimes called a buffer or a queue) to store segments if bandwidth is not currently available to transmit those segments. A queue has a finite capacity, however, and can overflow (that is, drop segments) in the event of sustained network congestion. In addition to TCP and UDP, Internet Control Message Protocol (ICMP) is another transport layer protocol you are likely to encounter. ICMP is used by utilities such as ping and traceroute, which are discussed in Chapter 10, ―Using Command-Line Utilities.‖ Layer 5: The Session Layer The session layer, as shown in Figure 2-12, is responsible for setting up, maintaining, and tearing down sessions. A session can be thought of as a conversation that needs to be treated separately from other sessions to avoid intermingling of data from different conversations. Figure 2-12 Layer 5: The Session Layer
- 136. • Setting up a session: Examples of the procedures involved in setting up a session include: • Checking user credentials (for example, username and password) • Assigning numbers to a session’s communications flows to uniquely identify each flow • Negotiating services required during the session • Negotiating which device begins sending data • Maintaining a session: Examples of the procedures involved in maintaining a session include: • Transferring data • Reestablishing a disconnected session • Acknowledging receipt of data • Tearing down a session: A session can be disconnected based on mutual agreement of the devices in the session. Alternately, a session might be torn down because one party disconnects (either intentionally or because of an error condition). In the event that one party disconnects, the other party can detect a loss of communication with that party and tear down its side of the session.
- 137. Table of Contents Title Page Copyright Page Acknowledgements About the Author Introduction Chapter 1 - Basic IOS Commands
- 138. Booting the Router Configuring a Router Using the show Command Chapter 2 - Managing a Cisco Internetwork Understanding the Internal Components of a Cisco Router Managing the Configuration Register Backing Up and Restoring the Cisco IOS Backing Up and Restoring the Cisco Configuration Using Cisco Discovery Protocol (CDP) Using Telnet Resolving Hostnames Checking Network Connectivity and Troubleshooting Using the sh processes Command Chapter 3 - IP Routing Routing Basics Routing Protocol Basics Routing Information Protocol (RIP) Chapter 4 - Enhanced IGRP (EIGRP) and Open Shortest Path First (OSPF) Understanding EIGRP Basics Understanding Open Shortest Path First (OSPF) Basics Configuring OSPF Verifying OSPF Configuration Chapter 5 - Layer-2 Switching and Spanning-Tree Protocol (STP) Switching Services Chapter 6 - Virtual LANs (VLANs) Understanding VLAN Basics Configuring VLANs Configuring VTP Telephony: Configuring Voice VLANs Chapter 7 - Security
- 139. Perimeter Routers, Firewalls, and Internal Routers Introduction to Access Lists Standard Access Lists Extended Access Lists Monitoring Access Lists Chapter 8 - Network Address Translation (NAT) When Do We Use NAT? Types of Network Address Translation NAT Names Configuring NAT Using SDM Chapter 9 - Cisco’s Wireless Technologies Introducing Wireless Technology Configuring Cisco Wireless Using the IOS Configuring Cisco Wireless Using the SDM/HTTP Chapter 10 - Internet Protocol Version 6 (IPv6) Why Do We Need IPv6? IPv6 Addressing and Expressions IPv6 Routing Protocols Migrating to IPv6 Verifying RIPng Verifying OSPFv3 Chapter 11 - Wide Area Networks (WANs) Introduction to Wide Area Networks High-Level Data-Link Control (HDLC) Protocol Point-to-Point Protocol (PPP) Introduction to Frame Relay Technology Chapter 12 - Cisco’s Security Device Manager (SDM) Configuring Your Router to Be Set Up Through the SDM Using the SDM to Manage the Flash Memory Using the SDM to Back Up, Restore, and Edit the Router’s Configuration Configuring LAN and WAN Interfaces and Verifying a Router Using SDM
- 140. Configuring RIP on a Router with SDM Configuring OSPF with the SDM What Does This Book Cover? This book covers everything you need to know in order to understand the CCNA exam objective commands. However, taking the time to study and practice with routers or a router simulator is the real key to success. You will learn the following information in this book: • Chapter 1 introduces you to the Cisco Internetwork Operating System (IOS) and command-line interface (CLI). In this chapter you will learn how to turn on a router and configure the basics of the IOS, including setting passwords, banners, and more. IP configuration using the Secure Device Manager (SDM) will be discussed in Chapter 12. • Chapter 2 provides you with the management skills needed to run a Cisco IOS network. Backing up and restoring the IOS, as well as router configuration, are covered, as are the troubleshooting command tools necessary to keep a network up and running. Chapter 12 will provide you the SDM configuration covered in this chapter. • Chapter 3 teaches you about IP routing. This is an important chapter, because you will learn how to build a network, add IP addresses, and route data between routers. You will also learn about static, default, and dynamic routing using RIP and RIPv2 (with a small touch of IGRP). • Chapter 4 dives into more complex dynamic routing with Enhanced IGRP and OSPF routing. • Chapter 5 gives you a background on layer-2 switching and how switches perform address learning and make forwarding and filtering decisions. Network loops and how to avoid them with the Spanning Tree Protocol (STP) will be discussed, as well as the 802.1w STP version. • Chapter 6 covers virtual LANs and how you can use them in your internetwork. This chapter also covers the nitty-gritty of VLANs and the different concepts and protocols used with VLANs, as well as troubleshooting. • Chapter 7 covers security and access lists, which are created on routers to filter the network. IP standard, extended, and named access lists are covered in detail. • Chapter 8 covers Network Address Translation (NAT). New information and all the configuration commands, troubleshooting, and verification commands needed to understand the NAT CCNA objectives are covered in this chapter. • Chapter 9 covers wireless technologies. This is an introductory chapter regarding wireless technologies as Cisco views wireless. Make sure you understand your basic wireless technologies such as access points and clients as well as the difference between 802.11a, b, and g. This chapter is more
- 141. technology based than configuration based to cover the current CCNA objectives. • Chapter 10 covers IPv6. This is a very fun chapter and has some great information. IPv6 is not the big, bad scary monster that most people think it is. IPv6 is an objective on this new exam, so study this chapter carefully. This chapter is more technology based then configuration based to cover the current CCNA objectives. Keep an eye out at www.lammle.com for up-to-the- minute updates. • Chapter 11 concentrates on Cisco wide area network (WAN) protocols. This chapter covers HDLC, PPP, and Frame Relay in depth. You must be proficient in all these protocols to be successful on the CCNA exam. • Chapter 12 covers SDM for basic router configures that we covered in Chapters 1, 2, 3, and 4. For up-to-the minute updates covering additions or modifications to the CCNA certification exams, as well as additional study tools and review questions, be sure to visit the Todd Lammle forum and website at www.lammle.com or www.sybex.com/go/ccnafastpass. Cisco Certified Network Associate (CCNA) The CCNA certification was the first in the new line of Cisco certifications and was the precursor to all current Cisco certifications. Now you can become a Cisco Certified Network Associate for the meager cost of this book and either one test at $150 or two tests at $125 each—although the CCNA exams are extremely hard and cover a lot of material, so you have to really know your stuff! Taking a Cisco class or spending months with hands-on experience is not out of the norm. Once you have your CCNA, you don’t have to stop there—you can choose to continue with your studies and achieve a higher certification, called the Cisco Certified Network Professional (CCNP). Someone with a CCNP has all the skills and knowledge he or she needs to attempt the routing and switching CCIE lab. Just becoming a CCNA can land you that job you’ve dreamed about. Why Become a CCNA? Cisco, not unlike Microsoft and Novell (Linux), has created the certification process to give administrators a set of skills and to equip prospective employers with a way to measure skills or match certain criteria. Becoming a
- 142. CCNA can be the initial step of a successful journey toward a new, highly rewarding, sustainable career. The CCNA program was created to provide a solid introduction not only to the Cisco Internetwork Operating System (IOS) and Cisco hardware but also to internetworking in general, making it helpful to you in areas that are not exclusively Cisco’s. At this point in the certification process, it’s not unrealistic that network managers—even those without Cisco equipment—require Cisco certifications for their job applicants. If you make it through the CCNA and are still interested in Cisco and internetworking, you’re headed down a path to certain success. What Skills Do You Need to Become a CCNA? To meet the CCNA certification skill level, you must be able to understand or do the following: • A CCNA certified professional can install, configure, and operate LAN, WAN, and wireless access services securely, as well as troubleshoot and configure small to medium networks (500 nodes or fewer) for performance. • This knowledge includes, but is not limited to, use of these protocols: IP, IPv6, EIGRP, RIP, RIPv2, OSPF, serial connections, Frame Relay, cable, DSL, PPPoE, LAN switching, VLANs, Ethernet, security, and access lists. How Do You Become a CCNA? The way to become a CCNA is to pass one little test (CCNA Composite exam 640-802). Then—poof!—you’re a CCNA. (Don’t you wish it were that easy?) True, it can be just one test, but you still have to possess enough knowledge to understand what the test writers are saying. However, Cisco has a two-step process that you can take in order to become a CCNA that may or may not be easier than taking one longer exam (this book is based on the one-step 640-802 method; however, this book has all the information you need to pass all three exams. The two-step method involves passing the following: • Exam 640-822: Interconnecting Cisco Networking Devices 1(ICND1) • Exam 640-816: Introduction to Cisco Networking Devices 2 (ICND2) I can’t stress this enough: It’s critical that you have some hands-on experience with Cisco routers. If you can get ahold of some 1841 or 2800 series routers, you’re set. But if you can’t, I’ve worked hard to provide hundreds of configuration examples throughout this book to help network administrators (or people who want to become network administrators) learn what they need to know to pass the CCNA exam.
- 143. Since the new 640-802 exam is so hard, Cisco wants to reward you for taking the two-test approach. Or so it seems anyway. If you take the ICND1 exam, you actually receive a certification called the Cisco Certified Entry Networking Technician (CCENT). This is one step toward your CCNA. To achieve your CCNA, you must still pass your ICND2 exam. Again, this book is written to help you study for all three exams. For Cisco-authorized hands-on training with CCSI Todd Lammle, please see www.globalnettraining.com. Each student will get hands-on experience by configuring at least three routers and two switches—no sharing of equipment! Where Do You Take the Exams? You may take any of the CCNA exams at any of the Pearson VUE authorized centers (www.vue.com) or call (877) 404-EXAM (3926). To register for a Cisco Certified Network Associate exam, follow these steps: 1. Determine the number of the exam you want to take. 2. Register with the nearest Pearson VUE testing center. At this point, you will be asked to pay in advance for the exam. At the time of this writing, the exam for the 640-802 is $150 and must be taken within one year of payment. You can schedule exams up to six weeks in advance or as late as the same day you want to take it—but if you fail a Cisco exam, you must wait five days before you will be allowed to retake the exam. If something comes up and you need to cancel or reschedule your exam appointment, contact Pearson VUE at least 24 hours in advance. 3. When you schedule the exam, you’ll get instructions regarding all appointment and cancellation procedures, the ID requirements, and information about the testing-center location. Tips for Taking Your CCNA Exams The CCNA Composite exam test contains about 55 questions and must be completed in 75 to 90 minutes or less. This information can change per exam. You must get a score of about 80 to 85 percent to pass this exam, but again, each exam can be different. Many questions on the exam have answer choices that at first glance look identical—especially the syntax questions! Remember to read through the choices carefully because close doesn’t cut it. If you get commands in the wrong order or forget one measly character, you’ll get the question wrong. So,
- 144. to practice, do the hands-on exercises at the end of this book’s chapters over and over again until they feel natural to you. Also, never forget that the right answer is the Cisco answer. In many cases, more than one appropriate answer is presented, but the correct answer is the one that Cisco recommends. On the exam, you’re always instructed to pick one, two, or three, never ―choose all that apply.‖ The latest CCNA exams may include the following test formats: • Multiple-choice single answer • Multiple-choice multiple answer • Drag-and-drop • Fill-in-the-blank • Router simulations In addition to multiple choice and fill-in response questions, Cisco Career Certifications exams may include performance simulation exam items. They do allow partial command responses. For example, show config, sho config, or sh conf would be acceptable. Router#show ip protocol or router#show ip prot would be acceptable. Here are some general tips for exam success: • Arrive early at the exam center so you can relax and review your study materials. • Read the questions carefully. Don’t jump to conclusions. Make sure you’re clear about exactly what each question asks. • When answering multiple-choice questions that you’re not sure about, use the process of elimination to get rid of the obviously incorrect answers first. Doing this greatly improves your odds if you need to make an educated guess. • You can no longer move forward and backward through the Cisco exams, so double check your answer before clicking Next since you can’t change your mind. After you complete an exam, you’ll get immediate, online notification of your pass or fail status, a printed Examination Score Report that indicates your pass or fail status, and your exam results by section. (The test administrator will give you the printed score report.) Test scores are automatically forwarded to Cisco within five working days after you take the test, so you don’t need to send your score to them. If you pass the exam, you’ll receive confirmation from Cisco, typically within two to four weeks, sometimes longer. This book covers everything CCNA related. For up-to-date information on Todd Lammle Cisco Authorized CCNA CCNP, CCSP, CCVP, and CCIE boot camps, please see www.lammle.com orwww.globalnettraining.com.
- 145. How to Contact the Author You can reach Todd Lammle through GlobalNet Training Solutions, Inc., (www.globalnettraining.com), his training and systems Integration Company in Dallas, Texas—or through his forum at www.lammle.com. Chapter 1 Basic IOS Commands This book starts by introducing you to the Cisco Internetwork Operating System (IOS). The IOS is what runs Cisco routers as well as some Cisco switches, and it’s what allows you to configure the devices. You use the command-line interface (CLI) to configure a router, and that is what I’ll show you in this chapter. The Cisco router IOS software is responsible for the following important tasks: • Carrying network protocols and functions • Connecting high-speed traffic between devices • Adding security to control access and stop unauthorized network use • Providing scalability for ease of network growth and redundancy • Supplying network reliability for connecting to network resources You can access the Cisco IOS through the console port of a router, from a modem into the auxiliary (or aux) port, or even through Telnet and Secure Shell (SSH). Access to the IOS command line is called an exec session. Once you have attached your console cable (this is a rolled cable, sometimes referred to as a rollover cable) to the router and have started your terminal software, you will be ready to power on the router. Assuming that this is a new router, it will have no configuration and thus will need to have, well, everything set up. In this chapter, first I’ll cover the power-on process of the router, and then I’ll introduce the setup script. For up-to-the minute updates for this chapter, please seewww.lammle.com Booting the Router
- 146. The following messages appear when you first boot or reload a router: Notice the following in the previous messages: • The type of router (2811) and the amount of memory (262,144KB) • The version of software the router is running (12.4, 13) • The interfaces on the router (two Fast Ethernet and four serial) Figure 1.1 shows a picture of an 1841 router, which is what is called anintegrated services router (ISR), just like the 2811 router output shown earlier. FIGURE 1.1 A Cisco 1841 router
- 147. An 1841 router holds most of the same interfaces as a 2800 router, but it’s smaller and less expensive. Setup Mode If the router has no initial configuration, you will be prompted to use setup mode to establish an initial configuration. You can also enter setup mode at any time from the command line by typing the command setup from something calledprivileged mode. Setup mode covers only some global commands and is generally just not helpful. Here is an example: You can exit setup mode at any time by pressing Ctrl+C. Router Configuration Modes One key to navigating the CLI is to always be aware of which router configuration mode you are currently in (see Table 1.1). You can tell which configuration mode you are in by watching the CLI prompt.
- 148. TABLE 1.1 Router Configuration Modes Once you understand the different modes, you will need to be able to move from one mode to another within the CLI. The commands in Table 1.2 allow you to navigate between the assorted CLI modes. TABLE 1.2 Moving Between Modes Editing and Help Features One difference between a good and a great CLI engineer is the ability to quickly edit the line being entered into the router. Great CLI engineers can quickly recall previously entered commands and modify them, which is often much quicker than reentering the entire command. Table 1.3 shows some of the editing commands most commonly used.
- 149. TABLE 1.3 CLI Editing Commands The CLI also provides extensive online help. Any great CLI engineer will have an excessively worn question-mark key on the keyboard! Table 1.4 shows some examples of using the online help. TABLE 1.4 Online Help Commands
- 150. Using the Question Mark The only command is the question mark; however, it does make a difference where you use it. When entering complex IOS commands, it is common to use the question mark repeatedly while entering the command, as in the following example: Using the Pipe The pipe (|) allows you to wade through all the configurations or other long outputs and get straight to your goods fast. Table 1.5 shows the pipe commands. TABLE 1.5 Pipe Commands Here’s an example of using the pipe command to view just interface information on a router:
- 151. Configuring a Router In the following sections, I’ll introduce the commands used to do basic router configuration. You’ll use these commands (or should use them) on every router you configure. Hostnames You can set the identity of the router with the hostname command. This is only locally significant, which means it has no bearing on how the router performs name lookups or how the router works on the internetwork. Table 1.6 shows the command for setting a router’s hostname. TABLE 1.6 Setting a Router Hostname Here’s an example of setting a hostname on a router: Banners You can create a banner to give anyone who shows up on the router exactly the information you want them to have. Make sure you’re familiar with these four available banner types: exec process creation banner, incoming terminal line
- 152. banner, login banner, and message of the day banner (all illustrated in Table 1.7). TABLE 1.7 Setting a Banner The following describes the various banners: MOTD banner The MOTD banner will be displayed whenever anyone attaches to the router, regardless of how they access the router. Exec banner You can configure a line activation (exec) banner to be displayed when an EXEC process (such as a line activation or incoming connection to a VTY line) is created. By simply starting a user exec session through a console port, you’ll activate the exec banner. Incoming banner You can configure a banner to be displayed on terminals connected to reverse Telnet lines. This banner is useful for providing instructions to users who use reverse Telnet. Login banner You can configure a login banner to be displayed on all connected terminals. This banner is displayed after the MOTD banner but before the login prompts. The login banner can’t be disabled on a per-line basis, so to globally disable it, you have to delete it with the no banner login command. Passwords You can use five passwords to secure your Cisco routers: console, auxiliary, Telnet (VTY), enable password, and enable secret. However, other commands are necessary to complete the password configurations on a router or switch, as shown in Table 1.8.
- 153. TABLE 1.8 Setting Passwords Setting Passwords Here’s an example of setting all your passwords and then encrypting them in the plain configuration file:
- 154. Some other console helpful commands include the following. This sets the console timeout in second and minutes from 0-35791: This redisplays interrupted console input:
- 155. Here’s an example of setting the exec-timeout and logging synchronous commands: Setting Up Secure Shell (SSH) Instead of Telnet, you can use Secure Shell, which creates a more secure session than the Telnet application that uses an unencrypted data stream. SSH uses encrypted keys to send data so that your username and password are not sent in the clear. Table 1.9 lists the commands. TABLE 1.9 SSH Commands Here’s an example of how you set up SSH on a router: 1. Set your hostname: 2. Set the domain name (both the hostname and domain name are required for the encryption keys to be generated): 3. Generate the encryption keys for securing the session:
- 156. 4. Set the maximum idle timer for an SSH session: 5. Set the maximum failed attempts for an SSH connection: 6. Connect to the VTY lines of the router: 7. Last, configure SSH and then Telnet as access protocols: If you do not use the keyword tel net at the end of the command string, then only SSH will work on the router. I suggest that you use just SSH if at all possible. Telnet is just too insecure for today’s networks.
- 157. A Practical Guide to Advanced Networking
- 158. Contents at a Glance Introduction 1 Network Infrastructure Design 2 Advanced Router Configuration I 3 Advanced Router Configuration II 4 Configuring Juniper Routers 5 Configuring and Managing the Network Infrastructure 6 Analyzing Network Data Traffic 7 Network Security 8 IPv6 9 Linux Networking 10 Internet Routing 11 Voice over IP Glossary Index Table of Contents Introduction Chapter 1 Network Infrastructure Design Chapter Outline Objectives Key Terms Introduction 1-1 Physical Network Design Core Distribution Layer Access Layer Data Flow Selecting the Media 1-2 IP Subnet Design IP Address Range Determining the Number of Subnetworks Needed for the Network Determining the Size or the Number of IP Host Addresses Needed for the Network IP Assignment 1-3 VLAN Network Virtual LAN (VLAN) VLAN Configuration VLAN Tagging 802.1Q Configuration Networking Challenge: Static VLAN Configuration
- 159. Configuring the HP Procurve Switch 1-4 Routed Network Router Gateway Address Network Segments Multilayer Switch Layer 3 Routed Networks Routed Port Configuration InterVLAN Routing Configuration Serial and ATM Port Configuration Summary Questions and Problems Chapter 2 Advanced Router Configuration I Chapter Outline Objectives Key Terms Introduction 2-1 Configuring Static Routing Gateway of Last Resort Configuring Static Routes Load Balancing and Redundancy Networking Challenge—Static Routes 2-2 Dynamic Routing Protocols Distance Vector Protocols Link State Protocols 2-3 Configuring RIPv2 Configuring Routes with RIP Configuring Routes with RIP Version 2 Networking Challenge—RIP 2-4 TFTP—Trivial File Transfer Protocol Configuring TFTP Summary Questions and Problems Chapter 3 Advanced Router Configuration II Chapter Outline Objectives Key Terms Introduction 3-1 Configuring Link State Protocols—OSPF Link State Protocols Configuring Routes with OSPF Load Balancing and Redundancy with OSPF
- 160. Networking Challenge—OSPF 3-2 Configuring Link State Protocols—IS-IS Configuring Routes with IS-IS Load Balancing and Redundancy with IS-IS Networking Challenge: IS-IS 3-3 Configuring Hybrid Routing Protocols—EIGRP Configuring Routes with EIGRP Load Balancing and Redundancy Networking Challenge: EIGRP 3-4 Advanced Routing Redistribution Route Redistribution into RIP Route Redistribution into OSPF Route Redistribution into EIGRP Route Redistribution into IS-IS 3-5 Analyzing OSPF ―Hello‖ Packets Summary Questions and Problems Chapter 4 Configuring Juniper Routers Chapter Outline Objectives Key Terms Introduction 4-1 Operational Mode 4-2 Router Configuration Mode Displaying the Router Interfaces Hostname Configuration Assigning an IP Address to an Interface 4-3 Configuring Routes on Juniper Routers Configure STATIC Routes on Juniper Routers Configure RIP on Juniper Routers Configure OSPF on Juniper Routers Configure IS-IS on Juniper Routers 4-4 Configuring Route Redistribution on Juniper Routers Summary Questions and Problems Chapter 5 Configuring and Managing the Network Infrastructure Chapter Outline Objectives Key Terms Introduction 5-1 Domain Name and IP Assignment 5-2 IP Management with DHCP
- 161. DHCP Data Packets DHCP Deployment 5-3 Scaling the Network with NAT and PAT Configuring NAT 5-4 Domain Name Service (DNS) DNS Tree Hierarchy DNS Resource Records Summary Questions and Problems Chapter 6 Analyzing Network Data Traffic Chapter Outline Objectives Key Terms Introduction 6-1 Protocol Analysis/Forensics Basic TCP/UDP Forensics ARP and ICMP 6-2 Wireshark Protocol Analyzer Using Wireshark to Capture Packets 6-3 Analyzing Network Data Traffic Configuring SNMP NetFlow 6-4 Filtering FTP Filtering Right-Click Filtering Logic Rules Filtering DHCP Summary Questions and Problems Chapter 7 Network Security Chapter Outline Objectives Key Terms Introduction 7-1 Denial of Service Distributed Denial of Service Attacks (DDoS) 7-2 Firewalls and Access Lists Network Attack Prevention Access Lists 7-3 Router Security Router Access Router Services Router Logging and Access-List
- 162. 7-4 Switch Security Switch Port Security Switch Special Features 7-5 Wireless Security 7-6 VPN Security VPN Tunneling Protocols Configuring a VPN Virtual Interface (Router to Router) Troubleshooting the VPN Tunnel Link Summary Questions and Problems Chapter 8 IPv6 Chapter Outline Objectives Key Terms Introduction 8-1 Comparison of IPv6 and IPv4 8-2 IPv6 Addressing 8-3 IPv6 Network Settings 8-4 Configuring a Router for IPv6 8-5 IPv6 Routing IPv6: Static IPv6: RIP IPv6: OSPF IPv6: EIGRP IPv6: IS-IS 8-6 Troubleshooting IPv6 Connection Summary Questions and Problems Chapter 9 Linux Networking Chapter Outline Objectives Key Terms Introduction 9-1 Logging On to Linux Adding a User Account 9-2 Linux File Structure and File Commands Listing Files Displaying File Contents Directory Operations File Operations Permissions and Ownership 9-3 Linux Administration Commands
- 163. The man (manual) Command The ps (processes) Command The su (substitute user) Command The mount Command The shutdown Command Linux Tips 9-4 Adding Applications to Linux 9-5 Linux Networking Installing SSH The FTP Client DNS Service on Linux Changing the Hostname 9-6 Troubleshooting System and Network Problems with Linux Troubleshooting Boot Processes Listing Users on the System Network Security Enabling and Disabling Boot Services 9-7 Managing the Linux System Summary Questions and Problems Chapter 10 Internet Routing Chapter Outline Objectives Key Terms Introduction 10-1 Internet Routing—BGP Configuring a WAN Connection Configuring an Internet Connection 10-2 Configuring BGP Configuring BGP Networking Challenge: BGP 10-3 BGP Best Path Selection 10-4 IPv6 over the Internet 10-5 Configure BGP on JUNIPER Routers Summary Questions and Problems Chapter 11 Voice over IP Chapter Outline Objectives Key Terms Introduction 11-1 The Basics of Voice over IP
- 164. 11-2 Voice over IP Networks Replacing an Existing PBX Tie Line Upgrading Existing PBXs to Support IP Telephony Switching to a Complete IP Telephony Solution 11-3 Quality of Service Jitter Network Latency Queuing QOS Configuration Example 11-4 Analyzing VoIP Data Packets Analyzing VoIP Telephone Call Data Packets 11-5 VoIP Security Summary Questions and Problems Key Terms Glossary Index About the Authors Jeffrey S. Beasley is with the Department of Engineering Technology and Surveying Engineering at New Mexico State University. He has been teaching with the department since 1988 and is the co-author of Modern Electronic Communication and Electronic Devices and Circuits, and the author ofNetworking. Piyasat Nilkaew is a network engineer with 15 years of experience in network management and consulting, and has extensive expertise in deploying and integrating multiprotocol and multivendor data, voice, and video network solutions on limited budgets. Dedications This book is dedicated to my family, Kim, Damon, and Dana. —Jeff Beasley This book is dedicated to Jeff Harris and Norma Grijalva. Not only have you given me my networking career, but you are also my mentors. You inspire me to think outside the box and motivate me to continue improving my skills. Thank you for giving me the opportunity of a lifetime. I am very grateful. —Piyasat Nilkaew Acknowledgments I am grateful to the many people who have helped with this text. My sincere thanks go to the following technical consultants:
- 165. • Danny Bosch and Matthew Peralta for sharing their expertise with optical networks and unshielded twisted-pair cabling, and Don Yates for his help with the initial Net-Challenge Software. • Abel Sanchez, for his review of the Linux Networking chapter. I also want to thank my many past and present students for their help with this book: • David Potts, Jonathan Trejo, and Nate Murillo for their work on the Net- Challenge Software. Josiah Jones, Raul Marquez Jr., Brandon Wise, and Chris Lascano for their help with the Wireshark material. Also, thanks to Wayne Randall and Iantha Finley Malbon for the chapter reviews. Your efforts are greatly appreciated. I appreciate the excellent feedback of the following reviewers: Phillip Davis, DelMar College, TX; Thomas D. Edwards, Carteret Community College, NC; William Hessmiller, Editors & Training Associates; Bill Liu, DeVry University, CA; and Timothy Staley, DeVry University, TX. My thanks to the people at Pearson for making this project possible: Dave Dusthimer, for providing me with the opportunity to work on this book, and Vanessa Evans, for helping make this process enjoyable. Thanks to Brett Bartow, Christopher Cleveland, and all the people at Pearson, and to the many technical editors for their help with editing the manuscript. Special thanks to our families for their continued support and patience. —Jeffrey S. Beasley and Piyasat Nilkaew About the Technical Reviewers Wayne Randall started working in the Information Technology field in 1994 at Franklin Pierce College (now Franklin Pierce University) in Rindge, NH, before becoming a Microsoft Certified Trainer and a consultant at Enterprise Training and Consulting in Nashua, NH. Wayne acquired his first certification in Windows NT 3.51 in 1994, became an MCSE in NT 4.0 in 1996, was a Certified Enterasys Network Switching Engineer in 2000, and then worked as a networking and systems consultant from 2001 to 2006 before becoming a director of IT for a privately held company. Wayne currently works for Bodycote, PLC, as a network engineer/solutions architect. Bodycote has 170 locations across 27 countries with 43 locations in North America. Wayne has taught for Lincoln Education since 2001 and developed curricula for it since 2011. Mr. Randall holds a BA in American Studies from Franklin Pierce University. Iantha Finley Malbon’s teaching career has spanned 20 years from middle school to collegiate settings and is currently a CIS professor at Virginia Union University. She is also an adjunct professor at ECPI University, having previously served as CIS Department Chair, teaching Cisco routing, networking, and Information Technology courses. She implemented the Cisco
- 166. Academy for Hanover Schools and was the CCAI for the Academy. She earned her master’s degree in Information Systems from Virginia Commonwealth University and bachelor’s degree in Technology Education from Virginia Tech. She holds numerous certifications including CCNA, Network+, A+, and Fiber Optic Technician. We Want to Hear from You! As the reader of this book, you are our most important critic and commentator. We value your opinion and want to know what we’re doing right, what we could do better, what areas you’d like to see us publish in, and any other words of wisdom you’re willing to pass our way. As the associate publisher for Pearson IT Certification, I welcome your comments. You can email or write me directly to let me know what you did or didn’t like about this book—as well as what we can do to make our books better. Please note that I cannot help you with technical problems related to the topic of this book. We do have a User Services group, however, where I will forward specific technical questions related to the book. When you write, please be sure to include this book’s title and author as well as your name, email address, and phone number. I will carefully review your comments and share them with the author and editors who worked on the book. Email: feedback@pearsonitcertification.com Mail: Dave Dusthimer Associate Publisher Pearson IT Certification 800 East 96th Street Indianapolis, IN 46240 USA Reader Services Visit our website and register this book at www.pearsonitcertification.com/register for convenient access to any updates, downloads, or errata that might be available for this book. Introduction This book looks at advanced computer networking. It first guides readers through network infrastructure design. The readers are then introduced to configuring static, RIPv2, OSPF, ISIS, EIGRP routing protocols, techniques for configuring Juniper router, managing the network infrastructure, analyzing network data traffic using Wireshark, network security, IPv6, Linux networking, Internet routing, and Voice over IP. After covering the entire text,
- 167. readers will have gained a solid knowledge base in advanced computer networks. In my years of teaching, I have observed that technology students prefer to learn ―how to swim‖ after they have gotten wet and taken in a little water. Then, they are ready for more challenges. Show the students the technology, how it is used, and why, and they will take the applications of the technology to the next level. Allowing them to experiment with the technology helps them to develop a greater understanding. This book does just that. Organization of the Text This textbook is adapted from the second edition of Networking. This third volume has been revised and reorganized around the needs of advanced networking students. This book assumes that the students have been introduced to the basics of computer networking. Throughout the text, the students are introduced to more advanced computer networking concepts. This involves network infrastructure design, advanced router configuration, network security, analyzing data traffic, Internet routing, and Voice over IP. Key Pedagogical Features • Chapter Outline, Key Terms, and Introduction at the beginning of each chapter clearly outline specific goals for the reader. An example of these features is shown in Figure P-1.
- 168. Figure P-1 • Net-Challenge Software provides a simulated, hands-on experience in configuring routers and switches. Exercises provided in the text (see Figure P- 2) and on the CD challenge readers to undertake certain router/ network configuration tasks. The challenges check the students’ ability to enter basic networking commands and set up router function, such as configuring the interface (Ethernet and Serial) and routing protocols (that is, static, RIPv2, OSPF, ISIS, EIGRP, BGP, and VLANs). The software has the look and feel of actually being connected to the router’s and switch console port.
- 169. Figure P-2 • The textbook features and introduces how to use the Wireshark Network Protocol Analyzer. Examples of using the software to analyze data traffic are included throughout the text, as shown inFigure P-3.
- 170. Figure P-3 • Numerous worked-out examples are included in every chapter to reinforce key concepts and aid in subject mastery, as shown in Figure P-4.
- 171. Figure P-4 • Key Terms and their definitions are highlighted in the margins to foster inquisitiveness and ensure retention. This is illustrated inFigure P-5.
- 172. Figure P-5 • Extensive Summaries, Questions, and Problems, as well as Critical Thinking Questions, are found at the end of each chapter, as shown inFigure P-6.
- 173. Figure P-6 • An extensive Glossary is found at the end of this book and offers quick, accessible definitions to key terms and acronyms, as well as an exhaustive Index (see Figure P-7).
- 174. Figure P-7 Accompanying CD-ROM The CD-ROM packaged with the text includes the captured data packets used in the text. It also includes the Net-Challenge Software, which was developed specifically for this text. Instructor Resources The Instructor’s Manual to accompany A Practical Guide to Advanced Networking, (ISBN: 978-0-132-88303-0) provides the entire book in PDF format along with instructor notes for each section within each chapter, recommending key concepts that should be covered in each chapter. Solutions to all Chapter Questions and Problems sections are also included. In addition, the instructor can also access 13 lab and lab-related exercises and a test bank with which to generate quizzes on the material found within the student edition of the book. Chapter 1. Network Infrastructure Design Chapter Outline Introduction
- 175. 1-1 Physical Network Design 1-2 IP Subnet Design 1-3 VLAN Network 1-4 Routed Network Summary Questions and Problems Objectives • Understand the purpose of the three layers of a campus network design • Understand the issue of data flow and selecting the network media • Develop techniques for IP allocation and subnet design • Understand the process of configuring a VLAN • Understand the issues of configuring the Layer 3 routed network Key Terms core distribution layer access layer CIDR ISP intranets NAT PAT Overloading supernet gateway broadcast domain flat network VLAN (virtual LAN) port-based VLAN tag-based VLAN protocol-based VLAN VLAN ID 802.1Q static VLAN dynamic VLAN show vlan vlan database vlan vlan_id show vlan name vlan-name interface vlan 1 show interface status trunk port Inter-Switch Link (ISL)
- 176. Switchport mode trunk switchport trunk encapsulation dot1q switchport trunk encapsulation isl switchport trunk allowed vlan vlan_id show interfaces trunk network address logical address router interface routing table subnet, NET multilayer switch (MLS) wire speed routing routed network Layer 3 network SONET WAN terminal monitor (term mon) terminal no monitor (term no mon) show ip interface brief (sh ip int br) no switchport secondary IP address InterVLAN routing router on a stick SVI DS CSU/DSU AMI B8ZS Minimum Ones Density HDLC PPP WIC VWIC service-module t1 show controller t1 slot/port ATM Virtual Path Connection (VPC) Virtual Channel Connection (VCC) SVC VPI VCI
- 177. Introduction The objective of this chapter is to examine the computer networking issues that arise when planning a campus network. The term campus network applies to any network that has multiple LANs interconnected. The LANs are typically in multiple buildings that are close to each other and interconnected with switches and routers. This chapter looks at the planning and designs of a simple campus network, including network design, IP subnet assignment, VLAN configuration, and routed network configuration. The basics of configuring the three layers of a campus LAN (core, distribution, and access) are first examined in Section 1-1. This section also addresses the important issues of data flow and selecting the proper network media. Section 1-2 examines IP allocation and subnet design. Section 1-3 discusses the VLAN network, including a step-by-step process of how to configure a VLAN, which provides an introduction to the basic switch commands and the steps for configuring a static VLAN. Section 1-4 examines the Layer 3 routed network. This section explores the functions of the router and includes configuration examples in different scenarios. 1-1. Physical Network Design Most campus networks follow a design that has core, distribution, and access layers. These layers, shown in Figure 1-1, can be spread out into more layers or compacted into fewer, depending on the size of these networks. This three- layer network structure is incorporated in campus networks to improve data handling and routing within the network. The issues of data flow and network media are also examined in this section.
- 178. Figure 1-1. The core, distribution, and access layers of a campus network Core The network core usually contains high-end Layer 3 switches or routers. Thecore is the heart, or backbone, of the network. The major portion of a network’s data traffic passes through the core. The core must be able to quickly forward data to other parts of the network. Data congestion should be avoided at the core, if possible. This means that unnecessary route policies should be avoided. An example of a route policy is traffic filtering, which limits what traffic can pass from one part of a network to another. Keep in mind that it takes time for a router to examine each data packet, and unnecessary route policies can slow down the network’s data traffic. Core The Backbone of the Network High-end routers and Layer 3 switches are typically selected for use in the core. Of the two, the Layer 3 switch is the best choice. A Layer 3 switch is essentially a router that uses electronic hardware instead of software to make routing decisions. The advantage of the Layer 3 switch is the speed at which it can make a routing decision and establish a network connection. Another alternative for networking hardware in the core is a Layer 2 switch. The Layer 2 switch does not make any routing decisions and can quickly make
- 179. network connection decisions based on the network hardware connected to its ports. The advantage of using the Layer 2 switch in the core is cost. The disadvantage is that the Layer 2 switch does not route data packets; however, high-speed Layer 2 switches are more affordable than high-speed routers and Layer 3 switches. An important design issue in a campus network and the core is redundancy.Redundancy provides for a backup route or network connection in case of a link failure. The core hardware is typically interconnected to all distribution network hardware, as shown in Figure 1-1. The objective is to ensure that data traffic continues for the entire network, even if a core networking device or link fails. Each layer beyond the core breaks the network into smaller networks with the final result being a group of networks that are capable of handling the amount of traffic generated. The design should thus incorporate some level of redundancy. Distribution Layer The distribution layer in the network is the point where the individual LANs connect to the campus network routers or Layer 3 switches. Routing and filtering policies are more easily implemented at the distribution layer without having a negative impact on the performance of the network data traffic. Also, the speed of the network data connections at the distribution layer is typically slower than at the core. For example, connection speeds at the core should be the highest possible, such as 1 or 10 gigabits, where the data speed connections at the distribution layer could be 100 Mbps or 1 gigabit. Figure 1-1 shows the connections to the access and core layers via the router’s Ethernet interfaces. Distribution Layer Point where the individual LANs connect together. Access Layer The access layer is where the networking devices in a LAN connect together. The network hardware used here is typically a Layer 2 switch. Remember, a switch is a better choice because it forwards data packets directly to destination hosts connected to its ports, and network data traffic is not forwarded to all hosts in the network. The exception to this is a broadcast where data packets are sent to all hosts connected to the switch. Access Layer Where the networking devices in a LAN connect together.
- 180. Note Hubs are not recommended at all in modern computer networks. Data Flow An important networking issue is how data traffic flows in the core, distribution, and access layers of a campus LAN. In reference to Figure 1-1, if computer A1 in LAN A sends data to computer D1 in LAN D, the data is first sent through the switch in LAN A and then to Router A in the distribution layer. Router A then forwards the data to the core switches, Switch A or Switch B. Switch A or Switch B then forwards the data to Router C. The data packet is then sent to the destination host in LAN D. The following are some questions often asked when setting up a network that implements the core, distribution, and access layers: • In what layer are the campus network servers (web, email, DHCP, DNS, and so on) located? This varies for all campus networks, and there is not a definitive answer. However, most campus network servers are located in the access layer. • Why not connect directly from Router A to Router C at the distribution layer? There are network stability issues when routing large amounts of network data traffic if the networks are fully or even partially meshed together. This means that connecting routers together in the distribution layer should be avoided. • Where is the campus backbone located in the layers of a campus network? The backbone of a campus network carries the bulk of the routed data traffic. Based on this, the backbone of the campus network connects the distribution and the core layer networking devices. Selecting the Media The choices for the media used to interconnect networks in a campus network are based on several criteria. The following is a partial list of things to consider: • Desired data speed • Distance for connections • Budget The desired data speed for the network connection is probably the first consideration given when selecting the network media. Twisted-pair cable works well at 100 Mbps and 1 Gbps and is specified to support data speeds of 10-gigabit data traffic. Fiber-optic cable supports LAN data rates up to 10 Gbps or higher. Wireless networks support data rates up to 200+ Mbps. The distance consideration limits the choice of media. CAT 6/5e or better have a distance limitation of 100 meters. Fiber-optic cable can be run for many kilometers, depending on the electronics and optical devices used. Wireless
- 181. LAN connections can also be used to interconnect networks a few kilometers apart. The available budget is always the final deciding factor when planning the design for a campus LAN. If the budget allows, fiber-optic cable is probably the best overall choice, especially in the high-speed backbone of the campus network. The cost of fiber is continually dropping, making it more competitive with lower-cost network media, such as twisted-pair cable. Also, fiber cable will always be able to carry a greater amount of data traffic and can easily grow with the bandwidth requirements of a network. Twisted-pair cable is a popular choice for connecting computers in a wired LAN. The twisted-pair technologies support bandwidths suitable for most LANs, and the performance capabilities of twisted-pair cable is always improving. Wireless LANs are being used to connect networking devices together in LANs where a wired connection is not feasible or mobility is the major concern. For example, a wireless LAN could be used to connect two LANs in a building together. This is a cost-effective choice if there is not a cable duct to run the cable to interconnect the LANs or if the cost of running the cable is too high. Also, wireless connections are playing an important role with mobile users within a LAN. The mobile user can make a network connection without having to use a physical connection or jack. For example, a wireless LAN could be used to enable network users to connect their mobile computers to the campus network. 1-2. IP Subnet Design Once the physical infrastructure for a network is in place, the next big step is to plan and allocate IP space for the network. Take time to plan the IP subnet design, because it is not easy to change the IP subnet assignments once they are in place. It is crucial for a network engineer to consider three factors before coming up with the final IP subnet design. These three factors are 1. The assigned IP address range 2. The number of subnetworks needed for the network 3. The size or the number of IP host addresses needed for the network The final steps in designing the IP subnet is to assign an IP address to the interface that will serve as the gateway out of each subnet. IP Address Range The IP address range defines the size of the IP network you can work with. In some cases, a classless interdomain routing (CIDR) block of public IP addresses might be allocated to the network by an ISP. For example, the block of IP address 206.206.156.0/24 could be assigned to the network. This case allocates 256 IP addresses to the 206.206.156.0 network. In another case, a CIDR block of private IP addresses, like 10.10.10.0/24, could be used. In this
- 182. case, 256 IP addresses are assigned to the 10.10.10.0 network. For established networks with an IP address range already in use, the network engineer generally has to work within the existing IP address assignments. With a brand new network, the engineer has the luxury of creating a network from scratch. In most network situations, an IP address block will have been previously assigned to the network for Internet use. The public IP addresses are typically obtained from the ISP (Internet service provider). This IP block of addresses could be from Class A, B, or C networks, as shown in Table 1-1. Table 1-1. Address Range for Each Class of Network CIDR Classless Interdomain Routing ISP Internet service provider: An organization that provides Internet access for the public. Today, only public Class C addresses are assigned by ISPs, and most of them are not even a full set of Class C addresses (256 IP addresses). A lot of ISPs partition their allotted IP space into smaller subnets and then, in turn, provide those smaller portions to the customers. The bottom line is the limited number of public IP addresses are now a commodity on the Internet, and it is important to note that there are fees associated with acquiring an IP range from an ISP. Not many institutions or businesses have the luxury of using public IP addresses inside their network anymore. This is because the growing number of devices being used in a network exceeds the number of public IP addresses assigned to them. The solution is that most networks are using private IP addresses in their internal network. Private addresses are IP addresses set aside for use in privateintranets. An intranet is an internal internetwork that provides file and resource sharing. Private addresses are not valid addresses for Internet use, because they have been reserved for internal use and are not routable on the Internet. However, these addresses can be used within a private LAN (intranet) to create the internal IP network.
- 183. Intranets Internetwork that provides file and resource sharing. NAT Network Address Translation. A technique used to translate an internal private IP address to a public IP address. PAT Port Address Translation. A port number is tracked with the client computer’s private address when translating to a public address. Overloading Where NAT translates the home network’s private IP addresses to a single public IP address. The private IP addresses must be translated to public IP addresses using techniques like NAT (Network Address Translation) or PAT (Port Address Translation) before being routed over the Internet. For example, computer 1 in the home network (see Figure 1-2) might be trying to establish a connection to an Internet website. The wireless router uses NAT to translate computer 1’s private IP address to the public IP address assigned to the router. The router uses a technique called overloading, where NAT translates the home network’s private IP addresses to the single public IP address assigned by the ISP. In addition, the NAT process tracks a port number for the connection. This technique is called Port Address Translation (PAT). The router stores the home network’s IP address and port number in a NAT lookup table. The port number differentiates the computer that is establishing a connection to the Internet because the router uses the same public address for all computers. This port number is used when a data packet is returned to the home network. This port number identifies the computer that established the Internet connection, and the router can deliver the data packet back to the correct computer. An example of this conversion is provided in Figure 1-3. This example shows three data connections originating from the home network of 192.168.0.0/24. A single 128.123.246.55 IP address is used for the Internet connection. Port address translation is being used to map the data packet back to the origination source. In this case, the port numbers are 1962, 1970, and 1973.
- 184. Figure 1-2. An example of a home computer connecting to the ISP Figure 1-3. This example shows the three data connections originating from the home network of 192.168.0.0/24 Determining the Number of Subnetworks Needed for the Network The use of private IP addresses is a viable technique for creating a large amount of IP addresses for intranet use. Obviously, there is a big difference when designing an IP network for a single network than there is when designing an IP network for multiple networks. When designing an IP network for one single network, things are quite simple. This type of configuration is typically found in the home, small office, or a small business environment where one IP subnet is allocated and only one small router is involved. For situations requiring multiple networks, each network must be sized accordingly. Therefore, the subnet must be carefully designed. In addition, networks with multiple subnets require a router or multiple routers with multiple routed network interfaces to interconnect the networks. For example, if the network engineer is using private addresses and needs to design for three different networks, one possibility is to assign 10.10.10.0/24 for the first
- 185. network, 172.16.0.0/24 for the second network, and 192.168.1.0/24 for the third network. Is this a good approach? Technically, this can be done, but it is probably not logically sound. It makes more sense to group these networks within the same big CIDR block. This will make it easier for a network engineer to remember the IP assignments and to manage the subnets. A better design is to assign 10.10.10.0/24 to the first network, 10.10.20.0/24 to the second network, and 10.10.30.0/24 to the third network. All three networks are all in the same ―10‖ network, which makes it easier for the network engineer to track the IP assignments. The term subnet and network are used interchangeably in multiple network environments. The term subnet usually indicates a bigger network address is partitioned and is assigned to smaller networks or subnets. Another design factor that the network engineer must address is the network size. Two questions that a good network engineer must ask are • How many network devices must be accommodated in the network? (Current demand) • How many network devices must be accommodated in the future? (Future growth) Simply put, the IP network must be designed to accommodate the current demand, and it must be designed to accommodate future growth. Once the size of a network is determined, a subnet can be assigned. In the case of a single network, the design is not too complicated. For example, if the network needs to be able to accommodate 150 network devices, an entire Class C address, like 192.168.1.0/24, can be assigned to the network. This will handle the current 150 network devices and leave enough room for growth. In this example, 104 additional IP address will be available for future growth. When allocating IP address blocks, a table like Table 1-2 can be used to provide the CIDR for the most common subnet masks and their corresponding number of available IP addresses. Table 1-2. CIDR—Subnet Mask-IPs Conversion
- 186. Even with a much smaller network, like the home network, where only a handful of network computers and peripherals are present, an entire Class C private address is generally allocated to the home network. In fact, most home routers are preconfigured with a private Class C address within the 192.168.0.0–192.168.0.255 range. This technique is user friendly and easy to use and sets aside private IP addresses for internal network use. This technique virtually guarantees that users will never have to worry about subnetting the CIDR block. For a bigger network that must handle more than 254 network devices, a supernet can be deployed. A supernet is when two or more classful contiguous networks are grouped together. The technique of supernetting was proposed in 1992 to eliminate the class boundaries and make available the unused IP address space. Supernetting allows multiple networks to be specified by one subnet mask. In other words, the class boundary could be overcome. For
- 187. example, if the network needs to be able to accommodate 300 network devices, two Class C networks, like 192.168.0.0/24 and 192.168.1.0/24, can be grouped together to form a supernet of 192.168.0.0/23, which can accommodate up to 510 network devices. As shown in Table 1-2, a /23 CIDR provides 512 available IP addresses. However, one IP is reserved for the network address and another one is reserved for the network broadcast address. Therefore, a /23 CIDR yields 512 – 2 = 510 usable host IP addresses. Supernet Two or more classful contiguous networks are grouped together. Determining the Size or the Number of IP Host Addresses Needed for the Network The problem with randomly applying CIDR blocks to Class A, B, and C addresses is that there are boundaries in each class, and these boundaries can’t be crossed. If a boundary is crossed, the IP address maps to another subnet. For example, if a CIDR block is expanded to include four Class C networks, all four Class C networks need to be specified by the same CIDR subnet mask to avoid crossing boundaries. The following example illustrates this. Example 1-1 Figure 1-4 shows three different networks with different size requirements. The needed capacity (number of devices) for each network is specified in the figure. Your task is to determine the CIDR block required for each network that will satisfy the number of expected users. You are to use Class C private IP addresses when configuring the CIDR blocks.
- 188. Figure 1-4. Three different networks Solution: For LAN A, a CIDR block that can handle at least 300 networking devices must be provided. In this case, two contiguous Class C networks of 192.168.0.0/24 and 192.168.1.0/24 can be grouped together to form a 192.168.0.0/23 network. Referring to Table 1-2, a /23 CIDR with a subnet mask of 255.255.254.0 provides 512 IP addresses which more than satisfies the required 300 networking devices. The next question is to determine what the network address is for LAN A. This can be determined by ANDing the 255.255.254.0 subnet mask with 192.168.0.0 and 192.168.1.0. This shows that applying the /23 [255.255.254.0] subnet mask to the specified IP address places both in the same 192.168.0.0 network. This also means that this CIDR block does not cross boundaries, because applying the subnet mask to each network address places both in the same 192.168.0.0 network. For LAN B1, the requirement is that a CIDR block that can handle 800 network devices must be provided. According to Table 1-2, a /22 CIDR yields 1,022 usable host IP addresses and is equivalent to grouping four Class C networks together. Therefore, a /22 CIDR can be used. The next decision is selecting the group of IP addresses to create the CIDR block and decide where the IP addresses should start. Recall that the 192.168.0.0 and 192.168.1.0 networks are being used to create the LAN A
- 189. CIDR block. Should LAN B1 start from 192.168.2.0/22, which is the next contiguous space? The answer is no. The 192.168.2.0/22 is still within the boundary of the 192.168.0.0/23 network. Remember, the requirement is that a CIDR block that can handle 800 network devices must be provided and that boundaries cannot be crossed, and the designer must be careful not to overlap the networks when assigning subnets to more than one network. In this case, when the /22 subnet mask (255.255.252.0) is applied to 192.168.2.0, this yields the network 192.168.0.0. The AND operation is shown: 192. 168. 2. 0 255. 255.252. 0 (/22) 192. 168. 0. 0 This happens to be the same network address as when the /23 CIDR subnet mask (255.255.254.0) is applied to any IP within the range of 192.168.0.0- 192.168.1.255, as shown: There is an overlap between 192.168.0.0/23 and 192.168.2.0/22. Moving to the next contiguous Class C of 192.168.3.0/22, we still find that it’s still in the 192.168.0.0: 192.168.3.0 255.255.252.0 (/22) 192.168.0.0 is still in the same subnet. Based on this information, the next Class C range 192.168.4.0/22 is selected. This yields a nonoverlapping network of 192.168.4.0, so the subnet 192.168.4.0/22 is a valid for this network: 192.168.4.0 255.255.252.0 (/22) 192.168.4.0 is not the same subnet; therefore, this is an acceptable CIDR block. Recall that the CIDR for LANB1 is a /22 and is equivalent to grouping four Class C networks. This means that LANB1 uses the following Class C networks: 192.168.4.0 192.168.5.0 192.168.6.0 192.168.7.0 The IP subnet design gets more complicated when designing multiple networks with different size subnets. This generally means that the subnet mask or the CIDR will not be uniformly assigned to every network. For example, one network might be a /25 network or /22, while another is a /30 network.
- 190. The next requirement is that a CIDR block that can handle 800 network devices must be tasked to assign a CIDR block to LAN B2. This LAN is a server network that houses a fixed number of servers. The number is not expected to grow beyond 80 servers. One easy approach is to assign a /24 CIDR to this network. This means that the next network is 192.168.8.0/24, which is the next nonoverlapping CIDR block after 192.168.4.0/22. The /24 CIDR gives 254 host IP addresses, but only 80 IP addresses are required. Another approach is to size it appropriately. According to Table 1-2, a good CIDR to use is a /25, which allows for 126 host IP addresses. Therefore, a network 192.168.8.0/25 can be used for this network. Assigning a 192.168.8.0/24 CIDR, which can accommodate 254 hosts, seems like a waste, because the network is expected to be a fixed size, and it will house no more than 80 servers. By assigning a 192.168.8.0/25 CIDR, enough room is left for another contiguous CIDR, 192.168.8.128/25. Obviously, this is a more efficient way of managing the available IP space. Last but not least is the interconnection shown in Figure 1-4. This is the router-to-router link between Router A and Router B. The interconnection usually gets the least attention, but it exists everywhere in the multiple networks environment. Nonetheless, a CIDR block has to be assigned to it. Because there are always only two interface IP addresses involved plus the network and broadcast address, giving an entire Class C address would definitely be a waste. Typically, a /30 CIDR is used for this type of connection. Therefore, a CIDR block for the interconnection between Router A and Router B can be 192.168.9.0/30. This yields two IP host addresses: one for Router A and one for Router B. The complete subnet assignment for Example 1-1 and Figure 1-4 is provided inTable 1-3. Table 1-3. Completed Design of Subnets for Figure 1-4 IP Assignment The next task requirement is that a CIDR block that can handle 800 network devices must be required to assign an IP address to each routed interface. This address will become the gateway IP address of the subnet. The gateway describes the networking device that enables hosts in a LAN to connect to
- 191. networks (and hosts) outside the LAN. Figure 1-5 provides an example of the gateway. Every network device within its subnet (LAN) will use this IP address as its gateway to communicate from its local subnet to devices on other subnets. The gateway IP address is preselected and is distributed to a network device by way of manual configuration or dynamic assignment. Figure 1-5. The gateway for a network Gateway Describes the networking device that enables hosts in a LAN to connect to networks (and hosts) outside the LAN. For LAN A in Example 1-1, the IP address 192.168.0.0 is already reserved as the network address, and the IP address 192.168.0.255 is reserved as the broadcast address. This leaves any IP address within the range 192.168.0.1– 192.168.0.254 available for use for the gateway address. Choosing the gateway IP address is not an exact science. Generally, the first IP address or the last IP address of the available range is chosen. Whatever convention is chosen, it should apply to the rest of the subnets for the ease of management. Once the gateway IP address is chosen, this IP address is reserved and is not to be used by any other devices in the subnet. Otherwise, an IP conflict will be introduced. The following is an example of how the gateway IP addresses could be assigned to the LANs inExample 1-1.
- 192. 1-3. VLAN Network This section examines the function of using a switch in a VLAN within the campus network. The terminology and steps for implementing VLANs will be presented first. The second part examines basic Cisco switch configuration and provides an introduction to the commands needed for configuring the VLAN. The third part of Section 1-3 demonstrates the commands needed to set up a static VLAN. Next is a discussion on VLAN tagging using 802.1Q. The section concludes with a look at configuring an HP Procurve switch. LANs are not necessarily restricted in size. A LAN can have 20 computers, 200 computers, or even more. Multiple LANs also can be interconnected to essentially create one large LAN. For example, the first floor of a building could be set up as one LAN, the second floor as another LAN, and the third floor another. The three LANs in the building can be interconnected into essentially one large LAN using switches, with the switches interconnected, as shown in Figure 1-6.
- 193. Figure 1-6. Three floors of a building interconnected using switches to form one large LAN Is it bad to interconnect LANs this way? As long as switches are being used to interconnect the computers, the interconnected LANs have minimal impact on network performance. This is true as long as there are not too many computers in the LAN. The number of computers in the LAN is an issue, because Layer 2 switches do not separate broadcast domains. This means that any broadcast sent out on the network (for example, the broadcast associated with an ARP request) will be sent to all computers in the LAN. Excessive broadcasts are a problem, because each computer must process the broadcast to determine whether it needs to respond; this essentially slows down the computer and the network. Broadcast Domain Any broadcast sent out on the network is seen by all hosts in this domain. A network with multiple LANs interconnected at the Layer 2 level is called a flat network. A flat network is where the LANs share the same broadcast domain. The use of a flat network should be avoided if possible for the simple reason that the network response time is greatly affected. Flat networks can be avoided by the use of virtual LANs (VLAN) or routers. Although both options can be used to separate broadcast domains, they differ in that the VLAN operates at the OSI Layer 2, while routers use Layer 3 networking to accomplish the task. The topic of a virtual VLAN is discussed next. Flat Network A network where the LANs share the same broadcast domain. Virtual LAN (VLAN) Obviously, if the LANs are not connected, then each LAN is segregated only to a switch. The broadcast domain is contained to that switch; however, this does not scale in a practical network, and it is not cost effective because each LAN requires its own Layer 2 switches. This is where the concept of virtual LAN (VLAN) can help out. A VLAN is a way to have multiple LANs co-exist in the same Layer 2 switch, but their traffic is segregated from each other. Even though they reside on the same physical switch, they behave as if they are on different switches (hence, the term virtual). VLAN compatible switches can communicate to each other and extend the segregation of multiple LANs throughout the entire switched network. A switch can be configured with a VLAN where a group of host computers and servers are configured as if they are in the same LAN, even if they reside across routers in separate LANs. Each
- 194. VLAN has its own broadcast domain. Hence, traffic from one VLAN cannot pass to another VLAN. The advantage of using VLANs is the network administrator can group computers and servers in the same VLAN based on the organizational group (such as Sales, Engineering) even if they are not on the same physical segment—or even the same building. VLAN (Virtual LAN) A group of host computers and servers that are configured as if they are in the same LAN, even if they reside across routers in separate LANs. There are three types of VLANs: port-based VLANs, tag-based VLANs, andprotocol-based VLANs. The port-based VLAN is one where the host computers connected to specific ports on a switch are assigned to a specific VLAN. For example, assume the computers connected to switch ports 2, 3, and 4 are assigned to the Sales VLAN 2, while the computers connected to switch ports 6, 7, and 8 are assigned to the Engineering VLAN 3, as shown in Figure 1-7. The switch will be configured as a port-based VLAN so that the groups of ports [2,3,4] are assigned to the sales VLAN while ports [6,7,8] belong to the Engineering VLAN. The devices assigned to the same VLAN will share broadcasts for that LAN; however, computers that are connected to ports not assigned to the VLAN will not share the broadcasts. For example, the computers in VLAN 2 (Sales) share the same broadcast domain and computers in VLAN 3 (Engineering) share a different broadcast domain. Figure 1-7. An example of the grouping for port-based VLANs Port-Based VLAN Host computers connected to specific ports on a switch are assigned to a specific VLAN. Tagged-Based VLAN Used VLAN ID based on 802.1Q. Protocol-Based VLAN Connection to ports is based on the protocol being used.
- 195. In tag-based VLANs, a tag is added to the Ethernet frames. This tag contains theVLAN ID that is used to identify that a frame belongs to a specific VLAN. The addition of the VLAN ID is based on the 802.1Q specification. The 802.1Q standard defines a system of VLAN tagging for Ethernet frames. An advantage of an 802.1Q VLAN is that it helps contain broadcast and multicast data traffic, which helps minimize data congestion and improve throughput. This specification also provides guidelines for a switch port to belong to more than one VLAN. Additionally, the tag-based VLANs can help provide better security by logically isolating and grouping users. VLAN ID Used to identify that a frame belongs to a specific VLAN. 802.1Q This standard defines a system of VLAN tagging for Ethernet frames. In protocol-based VLANs, the data traffic is connected to specific ports based on the type of protocol being used. The packet is dropped when it enters the switch if the protocol doesn’t match any of the VLANs. For example, an IP network could be set up for the Engineering VLAN on ports 6,7,8 and an IPX network for the Sales VLAN on ports 2,3, and 4. The advantage of this is the data traffic for the two networks is separated. There are two approaches for assigning VLAN membership: • Static VLAN: Basically a port-based VLAN. The assignments are created when ports are assigned to a specific VLAN. • Dynamic VLAN: Ports are assigned to a VLAN based on either the computer’s MAC address or the username of the client logged onto the computer. This means that the system has been previously configured with the VLAN assignments for the computer or the username. The advantage of this is the username and/or the computer can move to a different location, but VLAN membership will be retained. Static VLAN Basically, a port-based VLAN. Dynamic VLAN Ports are assigned to a VLAN based on either the computer’s MAC address or the username of the client logged onto the computer. VLAN Configuration This section demonstrates the steps for configuring a static VLAN. In this example, the ports for VLAN 2 (Sales) and VLAN 3 (Engineering) will be
- 196. defined. This requires that VLAN memberships be defined for the required ports. The steps and the commands will be demonstrated. The show vlan command can be used to verify what ports have been defined for the switch. By default, all ports are assigned to VLAN 1. An example using theshow vlan command is provided next. Click here to view code image SwitchA# show vlan VLAN Name Status Ports ---- -------------------------- --------- ----------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4 Fa0/5, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10 show vlan Used to verify what ports have been defined for the switch. This shows that all the FastEthernet interfaces on the switch are currently assigned to VLAN 1, which is a default VLAN. In the next step, two additional VLANs will be created for both Sales and Engineering. The two new VLANs will have the VLAN ID of 2 and 3 respectively, and each VLAN will be assigned a name associated to it. This is accomplished by modifying the VLAN database using thevlan database command, as shown in the next steps. vlan database The command used on older Cisco switches to enter the VLAN database. Click here to view code image SwitchA#vlan database SwitchA(vlan)#vlan 2 name Sales VLAN 2 modified: Name: Sales SwitchA(vlan)#vlan 3 name Engineering VLAN 3 modified: Name: Engineering On newer Cisco switches, users will get the following message that the commandvlan database is being deprecated: Click here to view code image % Warning: It is recommended to configure VLAN from config mode, as VLAN database mode is being deprecated. Please consult user documentation for configuring VTP/VLAN in config mode. Cisco has moved away from the VLAN database-style command to an IOS global command. Similarly to other IOS global commands, the switch must be in the configuration mode (config)#. However, the concept remains the same
- 197. that a VLAN must be created for it to be activated and ready for use. The steps for creating the VLAN on newer Cisco switches are as follows: Click here to view code image SwitchA# conf t SwitchA(config)#vlan 2 SwitchA(config-vlan)#name Sales SwitchA(config-vlan)#vlan 3 SwitchA(config-vlan)#name Engineering SwitchA(config-vlan)#exit SwitchA(config)#exit To start configuring a VLAN, one must specify which VLAN needs to be configured using the vlan [vlan_id] command. If the specific VLAN does not exist, this command will create the VLAN as well. As shown in the preceding example, the command vlan 2 is entered to configure vlan 2 and then the command name Sales is entered to configure the name associated to the VLAN. The similar steps are done for VLAN 3 with the name Engineering. vlan [vlan_id] The IOS global command used to create VLAN ID. The rest of the VLAN commands are almost identical in the older switches and newer switches. The next step is used to verify that the new VLANs have been created using the show vlan command: Click here to view code image Switch#show vlan VLAN Name Status Ports ---- -------------------------- --------- ----------------------------- 1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4 Fa0/5, Fa0/6, Fa0/7, Fa0/8 Fa0/9, Fa0/10 2 Sales active 3 Engineering active This shows that both the Sales and Engineering VLANs have been created. In the next steps, ports will be assigned to the newly created VLANs. This requires that the configuration mode be entered and each FastEthernet interface (port) must be assigned to the proper VLAN using the two commands switchport mode access and switchport access vlan vlan-id. An example is presented for FastEthernet interface 0/2 being assigned to VLAN 2 on a Cisco switch: Click here to view code image SwitchA#conf t Enter configuration commands, one per line. End with CNTL/Z. SwitchA(config)#int fa 0/2 SwitchA(config-if)#switchport mode access SwitchA(config-if)#switchport access vlan 2 SwitchA(config-if)#end
- 198. The next step is used to verify that FastEthernet 0/2 has been assigned to the Sales VLAN (VLAN2). This can be verified using the show vlan brief command, as shown. This command only displays the interfaces assigned to each VLAN: Click here to view code image SwitchA#sh vlan brief VLAN Name Status Ports ---- ----------------------------- --------- ------------------------ 1 default active Fa0/1, Fa0/3, Fa0/4, Fa0/5 Fa0/6, Fa0/7, Fa0/8, Fa0/9 Fa0/10 2 Sales active Fa0/2 The next steps are to assign ports 3 and 4 to the Sales VLAN (VLAN 2) and ports 6,7,8 to Engineering (VLAN 3). Once this is completed, the port assignments can be verified using the show vlan command, as shown: Click here to view code image SwitchA#show vlan VLAN Name Status Ports ---- ---------------------------- --------- ------------------------- 1 default active Fa0/1, Fa0/5, Fa0/9, Fa0/10 2 Sales active Fa0/2, Fa0/3, Fa0/4 3 Engineering active Fa0/6, Fa0/7, Fa0/8 You can look specifically at the assignments for only one of the VLANs by entering the command show vlan name vlan-name, where vlan-name is the name assigned to the VLAN. Note that the name is case-sensitive. You can also use the number of the VLAN instead of using the command show vlan id vlan-id. Examples of both are presented: show vlan name vlanname The command to look specifically at only one of the VLANs. Click here to view code image SwitchA#show vlan name Engineering VLAN Name Status Ports ---- -------------------------------- --------- --------------------- 3 Engineering active Fa0/6, Fa0/7, Fa0/8 Switch#show vlan id 3 VLAN Name Status Ports
- 199. ---- -------------------------------- --------- --------------------- 3 Engineering active Fa0/6, Fa0/7, Fa0/8 On Layer 2 switches, an IP address can be assigned to a VLAN interface. This merely assigns an IP address to a switch, so that a switch can communicate with other network devices on the same VLAN and vice-versa. The IP VLAN interface does not perform any routing functions when running as a layer 2 switch. As a matter of fact, the IP VLAN interface is not required in order for a switch to start forwarding packets and perform its other Layer 2 functions. By default, theinterface VLAN 1 is automatically created. The following command sequence demonstrates how to assign the IP address to the VLAN interface: interface VLAN 1 The default vlan for the switch. Click here to view code image SwitchA(config)# interface VLAN 1 SwitchA(config-if)# ip address 192.168.1.1 255.255.255.0 SwitchA(config-if)# no shutdown Note that the IP address is being set for VLAN 1. The interface for the switch is also enabled at this same point using the no shutdown command, as shown. In order for the interface VLAN to be up, at least one switch port in the VLAN must be up or have a physical link. The status of a switch port can be verified with the command show interface or, better yet, with the command show interface status. Although the command show interface shows detailed information of individual interface one at a time, the command show interface statusdisplays the status of all the switch ports including their speed, duplex, and VLAN, as shown. This gives a quick and precise look of the port status of a switch where port density is high. show interface status Used to verify the status of a switchport. Click here to view code image SwitchA#show interface status Port Name Status Vlan Duplex Speed Type Fa0/1 connected 1 a-full a-100 10/100BaseTX Fa0/2 connected 2 a-full a-100 10/100BaseTX Fa0/3 connected 2 a-full a-100 10/100BaseTX Fa0/4 connected 2 a-full a-100 10/100BaseTX Fa0/5 connected 1 a-full a-100
- 200. 10/100BaseTX Fa0/6 connected 3 a-full a-100 10/100BaseTX Fa0/7 connected 3 a-full a-100 10/100BaseTX Fa0/8 connected 3 a-full a-100 10/100BaseTX Fa0/9 connected 1 a-full a-100 10/100BaseTX Fa0/10 connected 1 a-full a-100 10/100BaseTX The overall configuration of the switch can be viewed using the show running-config (sh run) command, as shown. (Only a part of the configuration is displayed.) Click here to view code image Switch#sh run - - Building configuration... Current configuration : 1411 bytes ! version 12.1 no service pad service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname Switch ! ip subnet-zero ! spanning-tree mode pvst no spanning-tree optimize bpdu transmission spanning-tree extend system-id ! interface FastEthernet0/1 !- interface FastEthernet0/2 switchport access vlan 2 switchport mode access . . . . . . . . interface FastEthernet0/5 ! interface FastEthernet0/6 switchport access vlan 3 switchport mode access ! interface FastEthernet0/9 ! interface FastEthernet0/10 ! ! interface Vlan1 ip address 192.168.1.1 255.255.255.0
- 201. no ip route-cache ! ip http server ! line con 0 line vty 0 15 login end The running-configuration for the switch shows that the FastEthernet interfaces have been assigned to the proper VLANs. Additionally, this shows that an IP address has been assigned to the default interface VLAN1. This portion of the text has demonstrated the steps for creating a static VLAN. Both Sales and Engineering VLANs were created, and specific ports on the switch were assigned to the respective VLANs. Unassigned ports remained as part of the default VLAN 1. VLAN Tagging This section explores the concept of VLAN tagging (802.1Q) and demonstrates the steps required for this configuration. The concept of VLAN tagging can be explained using the example network shown in Figure 1-8. In this network, the Sales team is spread out in two different buildings. Therefore, the Sales VLAN network must be available in both buildings. Each building has its own network switch, and both switches are connected via one physical link. Figure 1-8. An example of a scenario with two VLANS spread across two buildings In a scenario like this, not only is it necessary to have the same Sales VLAN running on both building switches, it is also important to have members of the same VLAN being able to communicate with each other across buildings and to adhere to the same VLAN restrictions. To accomplish this, a technique called VLAN tagging is used. VLAN tagging is a technique deployed on a switch interface to carry Ethernet frames of multiple VLANs. The interface must connect to another switch port, router port, or network device that understands VLAN tagging, and both sides must agree on the VLAN tagging protocol. Trunk Port A switch interface or port configured to carry multiple VLANs.
- 202. Inter-Switch Link (ISL) The Cisco proprietary VLAN tagging protocol. The standard protocol for VLAN tagging is IEEE 802.1Q. This standard protocol is widely supported by every switch manufacturer, as well as Cisco. A switch interface or port configured to carry traffic for multiple VLANs is often referred to as a trunk port. The term was made famous by Cisco, and it is used explicitly as the VLAN tagging command in Cisco switches. Note that Cisco has its own proprietary VLAN tagging protocol called Inter-Switch Link (ISL). The big difference between ISL and 802.1Q is how the frame is treated. In ISL, every Ethernet frame is encapsulated within a 26-Byte header containing the VLAN ID and a 4 Byte CRC at the end. This makes the size of an ISL frame bigger than an 802.1Q frame, as discussed next. To accomplish the VLAN tagging of the Ethernet frames, IEEE 802.1Q simply inserts additional data to the Ethernet frame header, as shown in Figure 1-9. An 802.1Q tag is a 4-Byte tag field that is inserted between the Source Address field and the Ethernet Type/Length field. By inserting an additional 4-Byte field, the Ethernet frame size is increased. Its minimum frame size is now increased from 64 Bytes to 68 Bytes, and its maximum frame size is now increased from 1,518 Bytes to 1,522 Bytes. Figure 1-9 also provides a detailed calculation of the Ethernet frame size. Because of the additional tag field and the increased frame size, it is important that both sides of the link be compatible. Otherwise, the tagged Ethernet frames will not be understood and, therefore, the frames will be dropped by a non-802.1Q-compliant interface.
- 203. Figure 1-9. Typical Ethernet frame versus Ethernet frame with 802.1Q tag 802.1Q Configuration This section demonstrates the steps for configuring 802.1Q VLAN tagging. The 802.1Q VLAN tagging is configured at the switch interface that interconnects to another network switch. In this case, interface FastEthernet 0/1 of Switch A is selected as a 802.1Q VLAN tagging port or a trunk port. The following demonstrates how to configure an interface as a trunk port on a Cisco switch. First, the interface is assigned as a trunk port by the command switchport mode trunk. This essentially turns on trunking. The next step is to define the tagging protocol, which is 802.1Q, in this case. The command switchport trunk encapsulation dot1q is used. If ISL is used, the command would beswitchport trunk encapsulation isl. The next command, switchport trunk allowed vlan vlan-id, is optional, but it is useful in limiting VLANs that can be carried across the link.
- 204. switchport mode trunk Turns on trunking. switchport trunk encapsulation dot1q This command defines that 802.1Q tagging protocol is being used. switchport trunk encapsulation isl This command defines that the tagging protocol is ISL. switchport trunk allowed vlan vlan-id This command is used to limit the VLANs that can be carried across the link. Click here to view code image SwitchA#conf t Enter configuration commands, one per line. End with CNTL/Z. SwitchA(config)#int fa 0/1 SwitchA(config-if)#switchport mode trunk SwitchA(config-if)#switchport trunk encapsulation dot1q SwitchA(config-if)#switchport trunk allowed vlan 1,2 SwitchA(config-if)#end By default, all configured VLANs are allowed across the trunk port. In order for VLAN tagging to work properly, it is important to configure the same commands on SwitchB’s trunk port. To verify the 802.1Q configuration, the command show interfaces trunk can be used: show interfaces trunk This command is used to verify the 802.1Q configuration. Click here to view code image SwitchA#sh interfaces trunk Port Mode Encapsulation Status Native vlan Fa0/1 on 802.1q trunking 1 Port Vlans allowed on trunk Fa0/1 1,2 Port Vlans allowed and active in management domain Fa0/1 1,2 Port Vlans in spanning tree forwarding state and not pruned Fa0/1 1,2 Networking Challenge: Static VLAN Configuration Use the Net-Challenge Simulator Software included with the text’s companion CD-ROM to demonstrate that you can perform basic switch and static VLAN configuration and set up a trunk connection. Place the CD-ROM in your computer’s drive. Open the Net-Challenge folder, and click NetChallengeV3-2.exe. After the software is running, click theSelect Challenge button. This opens a Select Challenge drop-down menu. Select
- 205. the Chapter 1 - Static VLAN Configurationchallenge to open a checkbox that can be used to verify that you have completed all the tasks. Do the following: 1. Enter the privileged EXEC mode on the switch (password: Chile). 2. Enter the switch’s configuration mode: Router(config). 3. Set the hostname of the switch to switch-A. 4. Configure the IP address for VLAN 1 interface with the following: IP address: 10.10.20.250 Subnet mask: 255.255.255.0 5. Enable the VLAN 1 interface. 6. Use the command to display the current VLAN settings for the switch. 7. Issue the command that lets you modify the VLAN database. 8. Create a VLAN 2 named Sales. 9. Verify that a new Sales VLAN has been created. 10. Issue the command to enter the fa0/2 interface configuration mode. 11. Enter the sequence of commands that are used to assign interface fa0/2 to the Sales VLAN. 12. Enter the command that enables you to display the interface assigned to each VLAN. 13. Enter the command that enables you to view specifically the assignments for the Sales VLAN. 14. Issue the command that allows you to view the switch’s running- configuration. 15. Issue the command to turn on trunking for SwitchA. 16. Issue the command to set trunk encapsulation to 802.1Q. 17. Issue the command that enables VLAN 1 and VLAN 2 to be carried across the link. Configuring the HP Procurve Switch This should not come as a surprise to learn that many switch manufacturers follow a similar configuration path as the Cisco switches. A similar Cisco- styled command-line interface (CLI) is deployed by those manufacturers as well. The following is an example of how to configure an HP Procurve switch. The first step is to enter the configuration mode using the command configure. Next, the VLAN # is entered using the vlan 2 command. Finally, the VLAN is assigned a name from the (vlan-2) prompt using the command name-Sales: Click here to view code image SwitchHP# configure SwitchHP(config)#vlan 2 SwitchHP(vlan-2)#name Sales
- 206. The command show vlan also exists on the HP switches, but the output result is different than the one produced from Cisco switches. The HP’s show vlancommand does not provide ports with VLAN membership, while the Cisco command does: Click here to view code image SwitchHP# show vlan Status and Counters - VLAN Information Maximum VLANs to support : 8 Primary VLAN : DEFAULT_VLAN Management VLAN : 802.1Q VLAN ID Name Status Voice Jumbo -------------- ------------ ------------ ----- ----- 1 DEFAULT_VLAN Port-based No No 2 Sales Port-based No No On a Cisco switch, the VLAN membership is configured at the interface level. On an HP switch, it is configured at the VLAN level, where each VLAN contains its port members. This example shows how a VLAN membership is assigned on an HP switch: Click here to view code image SwitchHP# configure SwitchHP(config)#vlan 2 SwitchHP(vlan-2)#untagged 48 In VLAN 2, port 48 is configured as an untagged member. This means that the port is not a tagged VLAN port. It is essentially just a port-based VLAN. It was mentioned earlier that the HP’s command show vlan does not give much detail. To get more VLAN details, one must specify the VLAN ID. The show vlan 2command can be used to verify that port 48 has been assigned to the Sales VLAN (VLAN2): Click here to view code image SwitchHP# show vlan 2 Status and Counters - VLAN Information - Ports - VLAN 2 802.1Q VLAN ID : 2 Name : Sales Status : Port-based Voice : No Jumbo : No Port Information Mode Unknown VLAN Status ------------------- -------------------- ---------- --------- 48 Untagged Learn Up On HP switches and other switch manufacturers, the command syntax for enabling a port to carry 802.1Q tagged frames is basically the same. On HP switches, there is not a trunk command. The step is to simply assign tagging ability to the switch port by issuing the command tagged port_number. Because this is a non-Cisco switch, 802.1Q is the only VLAN tagging protocol that can be used. The following command
- 207. sequence demonstrates how to configure an interface port 24 on an HP switch as a 802.1Q VLAN tagging port: Click here to view code image SwitchHP# conf SwitchHP(config)# vlan 1 SwitchHP(vlan-1)# tagged 24 SwitchHP(vlan-1)# exit SwitchHP(config)# vlan 2 SwitchHP(vlan-2)# tagged 24 SwitchHP(vlan-2)# exit Unlike Cisco switches where an 802.1Q is configured at the interface level, the tagging configuration is done at the VLAN level on HP switches. Port 24 is designated as tagged port for both VLAN 1 and VLAN 2, which enables it to carry VLAN 1 and VLAN 2 frames. Generally, untagged ports belong to one specific VLAN, while tagged ports can belong to one or more VLANs. 1-4. Routed Network This section examines the Layer 3 network and how data is routed in the network. This section also introduces another Layer 3 device, the multilayer switch. You need to understand the advantages and disadvantages of this device. This section also introduces interVLAN configuration, which enables VLANs to communicate across networks. The section concludes with a look at both serial and ATM configurations. Some network engineers will argue that the serial and ATM technologies are a dying technology and are now considered obsolete. However, being obsolete does not mean they are nonexistent. These technologies are still being used throughout the world, and it is still an important topic. Router The router is a powerful networking device used to interconnect LANs. The router is a Layer 3 device in the OSI model, which means the router uses thenetwork address (Layer 3 addressing) to make routing decisions regarding forwarding data packets. In the OSI model, the Layer 3, or network, layer responsibilities include handling of the network address. The network address is also called a logical address, rather than being a physical address (such as the MAC address, which is embedded into the network interface card [NIC]). Thelogical address describes the IP address location of the network and the address location of the host in the network. Network Address Another name for the Layer 3 address. Logical Address This describes the IP address location of the network and the address location of the host in the network.
- 208. Essentially, the router is configured to know how to route data packets entering or exiting the LAN. This differs from the bridge and the Layer 2 switch, which use the Ethernet address for making decisions regarding forwarding data packets and only know how to forward data to hosts physically connected to their ports. Routers are used to interconnect LANs in a campus network. Routers can be used to interconnect networks that use the same protocol (for example, Ethernet), or they can be used to interconnect LANs that are using different Layer 2 technologies, such as an Ethernet, ATM, T1, and so on. Routers also make it possible to interconnect to LANs around the country and the world and interconnect to many different networking protocols. The router ports arebidirectional, meaning that data can enter and exit the same router port. Often, the router ports are called the router interface, which is the physical connection where the router connects to the network. Router Interface The physical connection where the router connects to the network. The network provided in Figure 1-10 is an example of a simple three-router campus network. This configuration enables data packets to be sent and received from any host on the network after the routers in the network have been properly configured. For example, computer A1 in LAN A could be sending data to computer D1 in LAN D. This requires that the IP address for computer D1 is known by the user sending the data from computer A1. The data from computer A1 will first travel to the switch where the data is passed to Router A via the FA0/0 FastEthernet data port. Router A will examine the network address of the data packet and use configured routing instructions stored in the router’s routing tables to decide where to forward the data. Router A determines that an available path to Router C is via the FA0/2 FastEthernet port connection. The data is then sent directly to Router C. Router C determines that the data packet should be forwarded to its FA0/0 port to reach computer D1 in LAN D. The data is then sent to D1. Alternatively, Router A could have sent the data to Router C through Router B via Router A’s FA0/1 FastEthernet port.
- 209. Figure 1-10. The three-router campus LAN Delivery of the information over the network was made possible by the use of an IP address and routing table. Routing tables keep track of the routes used for forwarding data to its destination. RouterA used its routing table to determine a network data path so computer A1’s data could reach computer D1 in LAN D. After the data packet arrived on Router C, an ARP request is issued by Router C to determine the MAC address of computer D1. The MAC address is then used for final delivery of the data to computer D1. Routing Table Keeps track of the routes to use for forwarding data to its destination. If Router A determines that the network path to Router C is down, Router A can route the data packet to Router C through Router B. After Router B receives the data packet from Router A, it uses its routing tables to determine where to forward the data packet. Router B determines that the data needs to be sent to Router C. Router B will then use its FA0/3 FastEthernet port to forward the data to Router C.
- 210. Gateway Address As previously discussed, the term gateway is used to describe the address of the networking device that enables the hosts in a LAN to connect to networks and hosts outside the LAN. For example, the gateway address for all hosts in LAN A will be 10.10.20.250. This address is configured on the host computer, as shown in Figure 1-11. Any IP packets with a destination outside the LAN A network will be sent to this gateway address. Note that the destination network is determined by the subnet mask. In this case, the subnet mask is 255.255.255.0. Figure 1-11. Network settings configuration for the default gateway Network Segments The network segment defines the networking link between two LANs. There is a segment associated with each connection of an internetworking device (for example, router-hub, router-switch, router-router). For example, the IP address for the network segment connecting LAN A to the router is 10.10.20.0. All hosts connected to this segment must contain a 10.10.20.x, because a subnet mask of 255.255.255.0 is being used. Subnet masking is fully explained in Network Essentials Chapter 6, ―TCP/IP.‖
- 211. Routers use the information about the network segments to determine where to forward data packets. For example, referring to Figure 1-10, the network segments that connect to Router A include 10.10.20.0 10.10.200.0 10.10.100.0 The segment is sometimes called the subnet or NET. These terms are associated with a network segment address, such as 10.10.20.0. In this case, the network is called the 10.10.20.0 NET. All hosts in the 10.10.20.0 NET will have a 10.10.20.x IP address. The network addresses are used when configuring the routers and defining which networks are connected to the router. Subnet, NET Other terms for the segment. According to Figure 1-11, all the computers in LAN A must have a 10.10.20.x address. This is defined by the 255.255.255.0 subnet mask. For example, computer A1 in LAN A will have the assigned IP address of 10.10.20.1 and a gateway address of 10.10.20.250. The computers in LAN B (see Figure 1-10) are located in the 10.10.10.0 network. This means that all the computers in this network must contain a 10.10.10.x IP address. In this case, the x part of the IP address is assigned for each host. The gateway address for the hosts in LAN B is 10.10.10.250. Notice that the routers are all using the same .250 gateway address. Remember, any valid IP address can be used for the gateway address, but it is a good design procedure to use the same number for number for all routers. In this case, .250 is being used. In other cases, it could be .1 or .254. The subnet mask is used to determine whether the data is to stay in the LAN or is to be forwarded to the default gateway provided by the router. The router uses its subnet mask to determine the destination network address. The destination network address is checked with the router’s routing table to select the best route to the destination. The data is then forwarded to the next router, which is the next hop address. The next router examines the data packet, determines the destination network address, checks its routing table, and then forwards the data to the next hop. If the destination network is directly connected to the router, it issues an ARP request to determine the MAC address of the destination host. Final delivery is then accomplished by forwarding the data using the destination host computer’s MAC address. Routing of the data through the networks is at Layer 3, and the final delivery of data in the network is at Layer 2.
- 212. Multilayer Switch So far, the topic of network switches revolves around their Layer 2 functionalities. Today, the scope of operations has changed for switches. Newer switch technologies are available to help further improve the performance of computer networks. This new development started with Layer 3 switches and now there are multilayer switches. The term used to describe these switches that can operate above the OSI Layer 2 is multilayer switches (MLS). An example is a Layer 3 switch. Layer 3 switches still work at Layer 2, but additionally work at the network layer (Layer 3) of the OSI model and use IP addressing for making decisions to route a data packet in the best direction. The major difference is that the packet switching in basic routers is handled by a programmed microprocessor. The multilayer switch uses application specific integrated circuits (ASIC) hardware to handle the packet switching. The advantage of using hardware to handle the packet switching is a significant reduction in processing time (software versus hardware). In fact, the processing time of multilayer switches can be as fast as the input data rate. This is called wire speed routing, where the data packets are processed as fast as they are arriving. Multilayer switches can also work at the upper layers of the OSI model. An example is a Layer 4 switch that processes data packets at the transport layer of the OSI model. Multilayer Switch (MLS) Operates at Layer 2, but functions at the higher layers. Wire Speed Routing Data packets are processed as fast as they arrive. Through this evolution, the line between routers and multilayer switches is getting more and more blurry. Routers were once considered the more intelligent device, but this is no longer true. With new developments, the multilayer switches can do almost everything the routers can. More importantly, most of the Layer 3 switch configuration commands are almost identical to the ones used on the routers. Routers tend to be more expensive when it comes to cost per port. Therefore, most of the traditional designs have a router connecting to a switch or switches to provide more port density. This can be expensive depending on the size of the network. So, there has been a shift toward deploying multilayer switches in the network LAN environment in place of routers. In this case, the routers and switches in Figure 1-10 then could all be replaced with multilayer switches. This also means there will be less network equipment to maintain, which reduces the maintenance cost and makes this a more cost-effective solution. With its greater port density, a multilayer switch can serve more clients than a router could. However, there is a common drawback for most multilayer switches: These devices only support
- 213. Ethernet. Other Layer 2 technologies, such as ATM, DSL,T1, still depend on routers for making this connection. Layer 3 Routed Networks As discussed previously, the hosts are interconnected with a switch or hub. This allows data to be exchanged within the LAN; however, data cannot be routed to other networks. Also, the broadcast domain of one LAN is not isolated from another LAN’s broadcast domain. The solution for breaking up the broadcast domains and providing network routing is to incorporate routing hardware into the network design to create a routed network. A routed network uses Layer 3 addressing for selecting routes to forward data packets, so a better name for this network is a Layer 3 network. Routed Network Uses Layer 3 addressing for selecting routes to forward data packets. Layer 3 Network Another name for a routed network. In Layer 3 networks, routers and multilayer switches are used to interconnect the networks and LANs, isolating broadcast domains and enabling hosts from different LANs and networks to exchange data. Data packet delivery is achieved by handing off data to adjacent routers until the packet reaches its final destination. This typically involves passing data packets through many routers and many networks. An example of a Layer 3 network is shown in Figure 1-10. This example has four LANs interconnected using three routers. The IP address for each networking device is listed. The physical layer interface on the router provides a way to connect the router to other networking devices on the network. For example, the FastEthernet ports on the router are used to connect to other FastEthernet ports on other routers or switches. Gigabit and 10-gigabit Ethernet ports are also available on routers to connect to other high-speed Ethernet ports (the sample network shown in Figure 1-10 includes only FastEthernet ports). Routers also contain other types of interfaces, such as serial interfaces and Synchronous Optical Network (SONET) interfaces. These interfaces were widely used to interconnect the router and the network to other wide-area networks (WAN). For example, connection to WANs requires the use of a serial interface or SONET interface to connect to a communications carrier, such as Sprint, AT&T, Century Link, and so on. The data speeds for the serial communication ports on routers can vary from slow (56 kbps) up to high-speed DS3 data rates (47+ Mbps), and the SONET could range from OC3 (155 Mbps), OC12 (622 Mbps), or even OC192 (9953 Mbps).
- 214. Synchronous Optical Network (SONET) Used to interconnect the router and the network to other WANs. WAN Wide-area network. Routed Port Configuration Routers can have Ethernet (10 Mbps), Fast Ethernet (100 Mbps), Gigabit Ethernet (1,000 Mbps), and 10 gigabit (10 GB), Serial, and ATM interfaces. These routers can have multiple interfaces, and the steps for configuring each interface are basically the same. Each interface is assigned a number. For example, a router could have three FastEthernet interfaces identified as FastEthernet 0/0 FastEthernet 0/1 FastEthernet 0/2 The notation 0/0 indicates the [interface-card-slot/port]. On Cisco’s routers, a routed port can be configured simply by assigning an IP address to the interface. Once an IP address and its subnet mask are assigned to the interface and the interface is enabled, a Layer 3 network is created. The interface IP address becomes the gateway for that network. To program the interface, the router must be in the configuration mode. The following demonstrates how to configure a router’s FastEthernet 0/0 port (FastEthernet 0/0, also listed as fa0/0 and FA0/0) as a routed interface. Click here to view code image Router(config)# int fa0/0 Router(config-if)# ip address 10.10.20.250 255.255.255.0 Router(config-if)#no shut 2w0d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up Notice that the router prompts you that the line protocol on interface FastEthernet 0/0 changed state to up. These log messages are always displayed when connecting via the console port. However, they are suppressed when it is a remote terminal session, like Telnet or SSH. To display log messages on the remote terminal, issue the command terminal monitor or term mon at the router prompt: terminal monitor (term mon) Displays log messages on the remote terminal. Router# term mon The log messages can be useful when bringing up a new connection. Sometimes, they can be annoying if the router is logging too many events. To disable the logging to the terminal, the command is terminal no
- 215. monitor or term no mon. One would think the command syntax would start with no, like typical Cisco command, but it is not so in this case: terminal no monitor (term no mon) Disables the logging to the terminal. Router# term no mon The command show ip interface brief (sh ip int brief) entered at the enable prompt (Router#) can be used to verify the status of the router interfaces. The following is an example: Click here to view code image Router# sh ip int brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 10.10.20.250 YES manual up up FastEthernet0/1 unassigned YES manual administratively down down FastEthernet0/2 unassigned YES manual administratively down down show ip interface brief (sh ip int brief) Verifies the status of the router interfaces. The output shows that the interface FastEthernet0/0 was configured with the IP address and its status is up. Because the FastEthernet0/1 and FastEthernet0/2 were not yet configured, their IP addresses are shown as unassigned and their interfaces are still administratively shut down. Also, a routed port can be assigned to a multilayer switch. This configuration is simple and the same as configuring a router port. The first step is to convert the native switch port to a router port. This is accomplished by issuing the commandno switchport on the desired switch interface. Then, the IP address and other configuration can be applied to the interface just like a typical router port: Click here to view code image SwitchA(config)# interface FastEthernet0/1 SwitchA(config-if)# no switchport SwitchA(config-if)# ip address 192.168.1.1 255.255.255.0 SwitchA(config-if)# no shutdown no switchport Converts the native switch port to a router port. One concept that is worth exploring is secondary IP address. The primary address is the IP address that is assigned to the interface. The secondary IP address is a way to support multiple IP addresses per router interface. Hence, it allows multiple Layer 3 networks to reside on the same physical link.
- 216. Secondary IP addresses can be useful when you want to add more networks without having to disturb the existing network or to use it as a transitional network for network migration. Some people might just want to run multiple logical subnets on one physical subnet. To add a secondary IP address to the interface, the command isip address [ip_address] [subnet_mask] secondary. The keyword secondaryis used to specify the secondary IP address. The secondary IP address configuration is as follows: Click here to view code image Router(config)# interface FastEthernet0/0 Router(config-if)# ip address 10.10.20.250 255.255.255.0 Router(config-if)# ip address 172.16.1.1 255.255.255.0 secondary Secondary IP Address Allows multiple Layer 3 networks to reside on the same physical link. In order to configure the secondary IP address, the primary IP address must exist first. There can be as many secondary IP addresses as needed. The secondary IP address cannot be verified with the show int or show ip int brief command. The results will only display the primary IP address information. InterVLAN Routing Configuration As previously discussed in Section 1-3, ―VLAN Network,‖ each VLAN is its own broadcast domain. It cannot forward traffic across its VLAN boundaries. However, it is almost impractical in today’s applications for a VLAN not to be able to communicate beyond itself. To enable communications among VLANs,InterVLAN routing is required. InterVLAN routing Enables communications among VLANs. router on a stick Eliminates connecting a link from each VLAN to a router port by utilizing a trunk or 802.1Q port. The most logical solution to route traffic between different VLANs is to introduce or create a Layer 3 routed network between them. One traditional way is to connect each VLAN to a router interface. Then, each router interface is configured as a different Layer 3 network. This enables VLANs to communicate and pass traffic via the Layer 3 IP network. For a few VLANs, this does not present an issue, but for a large number of VLANs, this could create some issues. This means that every VLAN will require a physical connection to a router port. Router ports are expensive, and this design can be costly as the number of VLANs increases and more physical links are required.
- 217. A more common and popular design is to implement a router on a stick. The router on a stick design eliminates connecting a link from each VLAN to a router port by utilizing a trunk or 802.1Q port. A single trunk port is connected to a router, and it passes the tagged VLAN traffic to the router, as depicted in Figure 1-12. Figure 1-12. Router on a stick topology This design requires that the router must be configured to accept the tagged VLANs. A Layer 3 network is then assigned to each VLAN coming to the router. To accomplish this, subinterfaces are created under the router interface at which the switch trunk port is terminated. The subinterface is a virtual interface, and its notation is a dot followed by the subinterface number. In the example provided, the subinterfaces are listed as FastEthernet0/0.1, 0.2, and 0.3. For the ease of programming, it is recommended to keep the subinterface number the same as the VLAN ID. Recall that the default VLAN is 1, the Sales VLAN is 2, and the Engineering VLAN is 3. The next step is to define the VLAN tagging encapsulation. In this case, it is dot1q, which essentially is 802.1Q. With the encapsulation, the appropriate VLAN ID is specified. Next, the IP address is assigned creating a routed Layer 3 network for a VLAN. The following example demonstrates how to configure a Cisco router for a 802.1Q interVLAN routing: Click here to view code image Router(config)#interface FastEthernet0/0 Router(config-if)#no ip address Router(config-if)#interface FastEthernet0/0.1 Router(config-if)#description Default VLAN Router(config-subif)#encapsulation dot1Q 1 Router(config-subif)#ip address 172.16.10.1 255.255.255.0 Router(config-subif)#interface FastEthernet0/0.2 Router(config-subif)#description Sales VLAN Router(config-subif)#encapsulation dot1Q 2
- 218. Router(config-subif)#ip address 172.16.20.1 255.255.255.0 Router(config-subif)#interface FastEthernet0/0.3 Router(config-subif)#description Engineering VLAN Router(config-subif)#encapsulation dot1Q 3 Router(config-subif)#ip address 172.16.30.1 255.255.255.0