Chapter6

Ch 6 - Chapter 6 Addressing the Network – IPv4

Objectives Explain the structure of IP addressing and demonstrate the ability to convert between 8-bit binary and decimal numbers Given an IPv4 address, classify by type and describe how it is used in the network Explain how addresses are assigned to networks by ISPs and within networks by administrators Determine the network portion of the host address and explain the role of the subnet mask in dividing networks Given IPv4 addressing information and design criteria, calculate the appropriate addressing components Use common testing utilities to verify and test network connectivity and operational status of the IP protocol stack on a host Ch 6 -

IPv4 Addressing Structure IPv4 is the current form of addressing used on the Internet Uses the dotted decimal structure to represent the 32-bit IP address Ch 6 -

IP Address Each device on a network must be uniquely defined assigned a 32-bit address used to identify the source and destination addresses The 32-bit address is written in a dotted decimal format each byte (or octet) is represented in decimal and separated by a dot Contains the network and host portions some portion of the higher-order bits represents the network address the number of bits in the host portion determines the number of hosts within the network Ch 6 - network host

Decimal Numbering System In the decimal numbering system, the radix (or base) is 10 has ten digits 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 245 = (2 x 100) + (4 x 10) + (5 x 1) Ch 6 - 10 2 10 1 10 0 100 10 1 2 4 5 200 + 40 + 5 245

Binary Numbering System In the binary numbering system, the radix (or base) is 2 has two digits 0 and 1 **11110101 = (1x128)+(1x64)+(1x32)+(1x16)+(0x8)+(1x4)+(0x2)+(1x1) = 245 Each octet has a minimum value of 0 and a maximum value of 255 Ch 6 -

Binary Number Characteristics The decimal value of any binary number is odd if the binary value of the least significant bit (LSB) is 1 The decimal value of any binary number is even if the binary value of the least significant bit (LSB) is 0 Ch 6 - X = 0 or 1 128 64 32 16 8 4 2 1 X X X X X X X 0 even LSB 128 64 32 16 8 4 2 1 X X X X X X X 1 odd LSB

Binary to Decimal Conversion Divide the 32 bits into 4 octets Convert each octet to decimal Add a “dot” between each decimal Ch 6 -

Decimal to Binary Conversion Start by determining if the decimal number is equal to or greater than the largest decimal value represented by the most significant bit (MSB) Ch 6 -

Dotted Decimal to Binary Conversion Separate and convert each decimal number separately Arrange each octet into the 32-bit address Ch 6 -

Types of Address Network address a way to refer to the network as a whole Broadcast address a special address used to send packets to every hosts in the network that shares the same network portion of the address Host address each host in the network has a unique address Ch 6 -

Network Prefix The prefix length is the number of bits in the address that gives the network (or subnetwork) portion /25 is the prefix length that indicates the first 25 bits are the network address => Subnet Increment = 128 Ch 6 -

5 Shortcuts to Remember /27=> 111 00000 – network portion , host portion Subnet Increment => 0,32,64,96,128,160,192,224 Subnet Mask 8 Subnet = 2 3 => 3 network bits IP AND Mask = Subnet/Network Ch 6 - Increment 128 64 32 16 8 4 2 1 Subnet Bits 1 2 3 4 5 6 7 8 Mask 128 192 224 240 248 252 254 255 Subnet Bits 1 2 3 4 5 6 7 8

Calculating Network , Hosts and Broadcast Addresses A network address contains all zeros in the host portion The first useable host address has a 0 for each host bit except the last bit, which is a 1, in the host portion The last useable host address has a 1 for each host bit except the Ch 6 - last bit, which is a 0, in the host portion The broadcast address contains all ones in the host portion

IP Address Example ( Popular Exam Question ) Last octet is 148 (10010100) 1001 is part of the network portion (28=8+8+8+4) 0100 is the host portion Ch 6 -

Unicast Transmission The process of sending a packet from one host to another host normal host-to-host communication Unicast packets use the host address of the destination device as the destination address and can be routed through an internetwork Ch 6 -

Broadcast Transmission The process of sending a packet from one host to all hosts in the network packet uses a special broadcast address as the destination address Used for locating special services/devices for which the address is not known or when the host needs to provide information to all hosts on the network Ch 6 - mapping upper-layer addresses to lower-layer addresses requesting an address exchanging routing information by routing protocols

Broadcast Transmission (cont’d) Directed broadcast is sent to all hosts on a specific network , usually a non-local network although routers do not forward directed broadcasts, they may be configured to do so Limited broadcast is used for communication that is limited to hosts on the local network packets used a destination address of 255.255.255.255 (all ones) packets addressed to the limited broadcast address will only appear on the local network Ch 6 -

Multicast Transmission The process of sending a packet from one host to a selected group of hosts designed to conserve bandwidth A special block of addresses from 224.0.0.0 to 239.255.255.255 is used for multicast groups addressing Ch 6 - Hosts that wish to receive particular multicast data are called multicast clients video and audio distribution routing information exchange by routing protocols software distribution news feeds

Reserved IPv4 Address IPv4 address range is from 0.0.0.0 to 255.255.255.255 not all these addresses can be used for host addresses in unicast transmission Multicast and experimental addresses are reserved for special purposes Ch 6 -

Public and Private Addresses Public addresses designated for use in networks that are accessible on the Internet Private addresses blocks of addresses that are used in private networks that require no or limited Internet access Ch 6 -

Private Addresses Three blocks of IP address space for private networks (online assessment question) 10.0.0.0 to 10.255.255.255 (10.0.0.0/8) 172.16.0.0 to 172.31.255.255 (172.16.0.0/12) 192.168.0.0 to 192.168.255.255 (192.168.0.0/16) Routers do not have routes to forward private address to the appropriate private networks Routers can use a service, called network address translation (NAT), to translate private addresses to public addresses NAT allows the hosts in a private network to “borrow” a public address for communicating to outside networks Ch 6 -

Special IPv4 Addresses Network and broadcast addresses the first, network, and last, broadcast, addresses cannot be assigned to hosts within each network Default route ( 0.0.0.0 /8) used as a “catch all” route when a more specific route is NOT available Loopback address( 127.0.0.1 ) a special address that hosts use to direct traffic to themselves entire address block, 127.0.0.0 to 127.255.255.255, is reserved Link-local addresses (Routers will not forward packets with link-local addresses) 169.254.0.0 to 169.254.255.255 (169.254.0.0/16) addresses are assigned to the local host by the operating system in environments where no IP configuration is available used in a small peer-to-peer network or for a host that could not automatically obtain an address from a DHCP server a host must not send an IPv4 link-local destination address to any router for forwarding and should set the TTL for these packets to 1 Ch 6 -

Special IPv4 Addresses (cont’d) TEST-NET address (Routers will not forward packets with TEST-NET addresses) address block 192.0.2.0 to 192.0.2.255 is reserved for teaching and learning purposes Ch 6 -

IP Address Classes Class A address designed to support very large networks with more than 16 million hosts first octet has a value of 1 to 126 used a fixed /8 prefix with the first octet to indicate the network address remaining three octets are used for host addresses Class B address designed to support the needs of moderate to large size networks with more than 65,000 hosts first octet has a value of 128 to 191 first and second octets represent the network Class C address ( 192 to 223 ) intended to provide addresses for small networks with a maximum of 254 hosts Ch 6 -

IP Address Classes (cont’d) first octet has a value of 192 to 223 first three octets represent the network Ch 6 -

Address Planning and Documentation Preventing duplication of address each host in an internetwork must have a unique address could assign a same address to more than one hosts Providing and controlling access access to resources , such as servers, can be controlled using Layer 3 address blocking access to a random address assignment for a server is difficult and client may not locate this resource Monitoring security and performance examine network traffic looking for addresses that are generating or receiving excessive packets Ch 6 -

Using Private Addresses Will there be more devices connected to the network than public addresses allocated by the ISP? Will the devices need to be accessed from outside the local network? If the devices that may be assigned private addresses require to access the Internet, is this network capable of providing a NAT service? Ch 6 -

Static Addressing for End Devices A network administrator must manually configure the network information for a host Static assignment of address can provide increased control of network resources time consuming to enter the information on each host Ch 6 - necessary to maintain an accurate list of address for each device to prevent address duplication

Dynamic Addressing for End Devices Preferred method of assigning IP addresses to hosts on large networks using DHCP address is leased for a period of time reduces the burden of support staff eliminates entry errors Ch 6 -

Assigning Addresses to Other Devices Addresses for servers and peripherals eg: Printer should have a static address servers and peripherals are concentration points for network traffic Addresses for hosts that are accessible from Internet the addresses for these devices should be static must have a public space address associated with it Addresses for intermediary devices, eg: Router, Switch intermediary devices are also a concentration point for network traffic may be used as hosts to configure, monitor, or troubleshoot network operation addresses are assigned manually to these devices Ch 6 -

Assigning Addresses to Other Devices (cont’d) Routers and firewalls each interface is assigned an address manually these devices are used for packet filtering Ch 6 -

IP Address Allocation Internet Assigned Numbers Authority ( IANA ) master holder of the IP address IP multicast and IPv6 are obtained directly from IANA Regional Internet Registries (RIR) remaining IPv4 address space is managed by RIR since mid 1990s Ch 6 -

Internet Service Providers ( ISP s) (Eg: Starhub, Singtel) Role supply a small number of useable IPv4 addresses (6 or 14) to their customers as part of their services Services DNS services, e-mail services and website Tiers Tier 1 ISPs provide reliability and speed with multiple connections to the Internet backbone Tier 2 ISPs generally focus on business customers Tier 3 ISPs focus on the retail and home market in a specific locale Ch 6 -

IPv6 Overview Improved packet handling Increased scalability and longevity QoS mechanisms Integrated security Ch 6 -

IPv6 Capabilities 128-bit hierarchical addressing to expand addressing capabilities Header format simplification (online assessment question) to improve packet handling Improved support for extensions and options for increased scalability, longevity and improved packet handling Flow labeling capabilities QoS mechanism Authentication and privacy capabilities to integrate security Ch 6 -

Subnet Mask The prefix and subnet mask are different ways of representing the same thing – the network portion of an IP address Ch 6 -

Subnet Mask Template Ch 6 - 128 64 32 16 8 4 2 1 Address bits 128 192 224 240 248 252 254 255 Possible Subnet Address 1 1 1 1 1 1 1 1

The AND Operation A host address is logically AND ed with its subnet mask to determine the network address to which the host is associated Routers use ANDing to determine an acceptable route for an incoming packet the destination network address is compared to the routes from the routing table Ch 6 - An originating host must determine if a packet should be sent directly to a host in a local network or be directed to the gateway

The ANDing Process Convert host address to binary Convert prefix to binary subnet mask AND each bit of host address with corresponding bit of mask Convert binary network address to decimal Ch 6 - 1 AND 1 = 1 0 AND 1 = 0 1 AND 0 = 0 0 AND 0 = 0

Basic Subnetting Subnetting allows for creating multiple logical networks from a single address block Subnets are created using one or more of the host bits as network bits done by extending the mask to borrow some of the bits from the host portion to create additional network bits Ch 6 -

Calculating Subnets and Hosts The number of subnets is calculated using 2 n , where n is the number of bits borrowed 2 1 = 2 subnets the more bits borrowed, the more subnets can be defined The number of useable hosts per subnet is calculated using 2 h - 2 where h is the number of host bits left 2 7 – 2 = 126 useable hosts per subnet with each bit borrowed, fewer host addresses are available per subnet Ch 6 -

Subnetting Example 1 Need to borrow a minimum of 2 host bits to cater for 3 subnets 2 2 = 4 subnets Ch 6 -

Subnetting Example 1 (cont’d) 6 host bits are left in the last octet 2 6 – 2 = 62 hosts per subnet Ch 6 -

Subnetting Example 2 Need to borrow a minimum of 3 host bits to cater for 6 subnets 2 3 = 8 subnets Ch 6 -

Subnetting Example 2 (cont’d) 5 host bits are left in the last octet 2 5 – 2 = 30 hosts per subnet Ch 6 -

Fixed Length Subnet Mask (FLSM) Using traditional subnetting or FLSM, each subnet is allocated the same number of host addresses these fixed size address block would be efficient if all subnets have the same requirements for the number of hosts Ch 6 - 2 5 – 2 = 30 hosts per subnet

Variable Length Subnet Mask ( VLSM ) VLSM was designed to maximize addressing efficiency each WAN link requires 2 host addresses Breaks up a subnet into a smaller subnet Ch 6 -

Using FLSM Standard subnetting would lock each subnet into blocks of 62 hosts 2 6 – 2 = 62 hosts to meet the highest number of hosts required Ch 6 -

Using FLSM (cont’d) The network has a given address block of 192.168.15.0/24 Need 6 host bits to support the largest user requirement The unused addresses are especially evident when the LAN routers support 10 users only Each WAN link has 60 unused address Ch 6 -

Using VLSM – Step 1 Calculate a subnet from the original 192.168.15.0/24 block to accommodate the largest LAN, i.e. 58 hosts Keep 6 host bits to cater for the 58 hosts 2 6 – 2 = 62 useable host addresses mask for last octet 11000000 2 bits are borrowed to create 4 possible subnets 192.168.15.0/26 (subnet 0) 192.168.15.64/26 (subnet 1) 192.168.15.128/26 (subnet 2) 192.168.15.192/26 (subnet 3) Assign subnet 0 (192.168.15.0/26) to this LAN 3 subnets left unused Ch 6 -

Using VLSM – Step 2 Consider the LAN with the next fewer hosts, i.e. 26 hosts Require 5 host bits to accommodate 26 hosts 2 5 – 2 = 30 useable host addresses mask for the last octet is 11100000 Use the next available address of 192.168.15.64/26 to create an address block for this subnet One more bit is borrowed from the above subnet 192.168.15.64/27 This subnet, 192.168.15.64/27, creates two more subnets 192.168.15.01000000/27 (subnet 0)  192.168.15.64/27 192.168.15.01100000/27 (subnet 1)  192.168.15.96/27 Assign the 192.168.15.64/27 to this LAN 1 subnet left unused Ch 6 -

Using VLSM – Step 3 Consider the LAN with the next fewer hosts, i.e. 10 hosts Require 4 host bits to accommodate 10 hosts 2 4 – 2 = 14 useable host addresses mask for the last octet is 11110000 Use the next available address of 192.168.15.96/27 to create an address block for this subnet One more bit is borrowed from the above subnet 192.168.15.96/28 This subnet, 192.168.15.96/28, creates two more subnets 192.168.15.01100000/28 (subnet 0)  192.168.15.96/28 192.168.15.01110000/28 (subnet 1)  192.168.15.112/28 Assign both these subnets to the LANs with the same number of hosts no subnet left Ch 6 -

Using VLSM – Step 4 Point-to-point WAN links require two host addresses Require two host bits to provide two host addresses 2 2 – 2 = 2 useable host addresses mask for the last octet is 11111100 Use the next available address of 192.168.15.128/26 to create an address block for this subnet Four more bits are borrowed from the above subnet 192.168.15.128/30 This subnet, 192.168.15.128/30, creates 16 more subnets 192.168.15.10000000/30 (subnet 0)  192.168.15.128/30 192.168.15.10000100/30 (subnet 1)  192.168.15.132/30 192.168.15.10001000/30 (subnet 2)  192.168.15.136/30 192.168.15.10001100/30 (subnet 3)  192.168.15.140/30 Ch 6 -

Using VLSM – Step 5 Calculate the address range and broadcast address for each subnet Document the host requirements, subnet addresses, address range, broadcast addresses and network prefix Ch 6 -

Using VLSM – Network Diagram Ch 6 -

Testing Connectivity Ping is a utility for testing IP connectivity between hosts sends out requests for responses from a specified host address provides a display output with a summary of the responses including the success rate and average round-trip time uses Internet Control Message Protocol ( ICMP ), a Layer 3 protocol (Network) Source device sends an ICMP echo request datagram to the destination device destination device responds with an ICMP echo reply if it receives the echo request ping measures the time taken for the reply Ch 6 - echo request echo reply source destination

Testing Local TCP/IP Stack Ch 6 -

Testing Connectivity to Local Gateway Test the host’s connectivity to the router interface Verify the correct address is configured as the default gateway Ch 6 - Security applied to the router interface may prevent it from responding to echo requests

Testing Connectivity to Remote LAN The ping command can also be used to verify the availability or reachability of a remote device Lack of ping response could be due to security restrictions and not because of non-operational elements of the network Ch 6 -

Testing The Path Traceroute , or tracert , is a utility to observe the path between two hosts The trace generates a list of hops that were successfully reached along the path if the data reaches the destination, the trace lists the interface on every router in the path if the data fails at some hop along the way, the trace lists the address of the last router that responded An asterisk (*) is used to indicate a lost packet Traceroute makes use of the TTL field the initial value in the TTL field in the first message is set to 1, allowing a single hop to the first router traceroute then progressively increments the TTL field for each message until the destination is reached Ch 6 -

ICMP IP uses the services of ICMP to send messages in the event of certain errors ICMP messages provide feedback about issues related to the processing of IP packets under certain conditions ICMP messages are not intended to make IP reliable ICMP provides control and error messages host confirmation – echo request and echo reply unreachable destination or service time exceeded route redirection source quench ICMP messages are often not allowed for security reasons Ch 6 -

Chapter6

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Chapter6 (20)

Recently uploaded (20)

Chapter6

Editor's Notes