Chapter1 introductiontoscalingnetworks

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CHAPTER # 1: INTRODUCTION TO SCALING NETWORKS
1.0.1.1 Introduction
As a business grows, so does its networking requirements. Businesses rely on the network
infrastructure to provide mission-critical services. Network outages can result in lost revenue
and lost customers. Network designers must design and build an enterprise network that is
scalable and highly available.
This chapter introduces strategies that can be used to systematically design a highly functional
network, such as the hierarchical network design model, the Cisco Enterprise Architecture, and
appropriate device selections. The goals of network design are to limit the number of devices
impacted by the failure of a single network device, provide a plan and path for growth, and
create a reliable network.
1.1 Implementing a Network Design
1.1.1 Hierarchical Network Design
1.1.1.1 The Need to Scale the Network
Businesses increasingly rely on their network infrastructure to provide mission-critical services.
As businesses grow and evolve, they hire more employees, open branch offices, and expand
into global markets. These changes directly affect the requirements of a network. A large
business environment with many users, locations, and systems is referred to as an enterprise.
The network that is used to support the business enterprise is called an enterprise network.
An enterprise network must support the exchange of various types of network traffic, including
data files, email, IP telephony, and video applications for multiple business units. All enterprise
networks must:
 Support critical applications
 Support converged network traffic
 Support diverse business needs
 Provide centralized administrative control

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1.1.1.2 Enterprise Business Devices
Users expect enterprise networks to be up 99.999 percent of the time. Outages in the enterprise
network prevent the business from performing normal activities, which can result in a loss of
revenue, customers, data, and opportunities.
To obtain this level of reliability, high-end, enterprise class equipment is commonly installed in
the enterprise network. Designed and manufactured to more stringent standards than lower-end
devices, enterprise equipment moves large volumes of network traffic.
Enterprise class equipment is designed for reliability, with features such as redundant power
supplies and failover capabilities. Failover capability refers to the ability of a device to switch
from a non-functioning module, service or device, to a functioning one with little or no break in
service.
Purchasing and installing enterprise class equipment does not eliminate the need for proper
network design.
1.1.1.3 Hierarchical Network Design
To optimize bandwidth on an enterprise network, the network must be organized so that traffic
stays local and is not propagated unnecessarily onto other portions of the network. Using the
three-layer hierarchical design model helps organize the network.
This model divides the network functionality into three distinct layers, as shown in Figure below:
 Access layer
 Distribution layer
 Core layer
Each layer is designed to meet specific functions.

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The access layer provides connectivity for the users. The distribution layer is used to forward
traffic from one local network to another. Finally, the core layer represents a high-speed
backbone layer between dispersed networks. User traffic is initiated at the access layer and
passes through the other layers if the functionality of those layers is required.
Even though the hierarchical model has three layers, some smaller enterprise networks may
implement a two-tier hierarchical design. In a two-tier hierarchical design, the core and
distribution layers are collapsed into one layer, reducing cost and complexity, as shown in
below.
1.1.1.4 Cisco Enterprise Architecture
The Cisco Enterprise Architecture divides the network into functional components while still
maintaining the core, distribution, and access layers. The primary Cisco Enterprise Architecture
modules include:
 Enterprise Campus
 Enterprise Edge
 Service Provider Edge
 Remote
Enterprise Campus
The Enterprise Campus consists of the entire campus infrastructure, to include the access,
distribution, and core layers. The access layer module contains Layer 2 or Layer 3 switches to
provide the required port density. Implementation of VLANs and trunk links to the building
distribution layer occurs here. Redundancy to the building distribution switches is important. The
distribution layer module aggregates building access using Layer 3 devices. Routing, access
control, and QoS are performed at this distribution layer module. The core layer module
provides high-speed interconnectivity between the distribution layer modules, data center server
farms, and the enterprise edge. Redundancy, fast convergence, and fault tolerance are the
focus of the design in this module.

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In addition to these modules, the Enterprise Campus can include other sub-modules such as:
 Server Farm and Data Center Module - This area provides high-speed connectivity
and protection for servers. It is critical to provide security, redundancy, and fault
tolerance. The network management systems monitor performance by monitoring device
and network availability.
 Services Module - This area provides access to all services, such as IP Telephony
services, wireless controller services, and unified services.
Enterprise Edge
The Enterprise Edge consists of the Internet, VPN, and WAN modules connecting the enterprise
with the service provider's network. This module extends the enterprise services to remote sites
and enables the enterprise to use Internet and partner resources. It provides QoS, policy
reinforcement, service levels, and security.
Service Provider Edge
The Service Provider Edge provides Internet, Public Switched Telephone Network (PSTN), and
WAN services.
All data that enters or exits the Enterprise Composite Network Model (ECNM) passes through
an edge device. This is the point that all packets can be examined and a decision made whether
the packet should be allowed on the enterprise network. Intrusion detection systems (IDS) and
intrusion prevention systems (IPS) can also be configured at the enterprise edge to protect
against malicious activity.
1.1.1.5 Failure D omains
A well-designed network not only controls traffic, but also limits the size of failure domains. A
failure domain is the area of a network that is impacted when a critical device or network service
experiences problems.
The function of the device that initially fails determines the impact of a failure domain. For
example, a malfunctioning switch on a network segment normally affects only the hosts on that
segment. However, if the router that connects this segment to others fails, the impact is much
greater.
The use of redundant links and reliable enterprise-class equipment minimize the chance of
disruption in a network. Smaller failure domains reduce the impact of a failure on company
productivity. They also simplify the troubleshooting process, thereby, shortening the downtime
for all users.
Limiting the Size of Failure Domains
Because a failure at the core layer of a network can have a potentially large impact, the network
designer often concentrates on efforts to prevent failures. These efforts can greatly increase the
cost of implementing the network. In the hierarchical design model, it is easiest and usually least
expensive to control the size of a failure domain in the distribution layer. In the distribution layer,
network errors can be contained to a smaller area; thus, affecting fewer users. When using

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Layer 3 devices at the distribution layer, every router functions as a gateway for a limited
number of access layer users.
Switch Block Deployment
Routers, or multilayer switches, are usually deployed in pairs, with access layer switches evenly
divided between them. This configuration is referred to as a building, or departmental, switch
block. Each switch block acts independently of the others. As a result, the failure of a single
device does not cause the network to go down. Even the failure of an entire switch block does
not affect a significant number of end users.

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1.1.2 Expanding the Network
1.1.2.1 Design for Scalability
To support an enterprise network, the network designer must develop a strategy to enable the
network to be available and to scale effectively and easily. Included in a basic network design
strategy are the following recommendations:
 Use expandable, modular equipment or clustered devices that can be easily upgraded to
increase capabilities. Device modules can be added to the existing equipment to support
new features and devices without requiring major equipment upgrades. Some devices
can be integrated in a cluster to act as one device to simplify management and
configuration.
 Design a hierarchical network to include modules that can be added, upgraded, and
modified, as necessary, without affecting the design of the other functional areas of the
network. For example, creating a separate access layer that can be expanded without
affecting the distribution and core layers of the campus network.
 Create an IPv4 or IPv6 address strategy that is hierarchical. Careful IPv4 address
planning eliminates the need to re-address the network to support additional users and
services.
 Choose routers or multilayer switches to limit broadcasts and filter other undesirable
traffic from the network. Use Layer 3 devices to filter and reduce traffic to the network
core.
More advanced network design requirements include:
 Implementing redundant links in the network between critical devices and between
access layer and core layer devices.
 Implementing multiple links between equipment, with either link aggregation
(EtherChannel) or equal cost load balancing, to increase bandwidth. Combining multiple
Ethernet links into a single, load-balanced EtherChannel configuration increases
available bandwidth. EtherChannel implementations can be used when budget
restrictions prohibit purchasing high-speed interfaces and fiber runs.
 Implementing wireless connectivity to allow for mobility and expansion.
 Using a scalable routing protocol and implementing features within that routing protocol
to isolate routing updates and minimize the size of the routing table.
1.1.2.2 Planning for Redundancy
Implementing Redundancy
For many organizations, the availability of the network is essential to supporting business
needs. Redundancy is an important part of network design for preventing disruption of network
services by minimizing the possibility of a single point of failure. One method of implementing
redundancy is by installing duplicate equipment and providing failover services for critical
devices.
Another method of implementing redundancy is redundant paths. Redundant paths offer
alternate physical paths for data to traverse the network. Redundant paths in a switched
network support high availability. However, due to the operation of switches, redundant paths in

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a switched Ethernet network may cause logical Layer 2 loops. For this reason, Spanning Tree
Protocol (STP) is required.
STP allows for the redundancy required for reliability, but eliminates the switching loops. It does
this by providing a mechanism for disabling redundant paths in a switched network until the path
is necessary, such as when failures occur. STP is an open standard protocol, used in a
switched environment to create a loop-free logical topology.
1.1.2.3 Increasing Bandwidth
Implementing EtherChannel
In hierarchical network design, some links between access and distribution switches may need
to process a greater amount of traffic than other links. As traffic from multiple links converges
onto a single, outgoing link, it is possible for that link to become a bottleneck. Link aggregation
allows an administrator to increase the amount of bandwidth between devices by creating one
logical link made up of several physical links. EtherChannel is a form of link aggregation used in
switched networks.
EtherChannel uses the existing switch ports; therefore, additional costs to upgrade the link to a
faster and more expensive connection are not necessary. The EtherChannel is seen as one
logical link using an EtherChannel interface. Most configuration tasks are done on the
EtherChannel interface, instead of on each individual port, ensuring configuration consistency
throughout the links. Finally, the EtherChannel configuration takes advantage of load balancing
between links that are part of the same EtherChannel, and depending on the hardware platform,
one or more load-balancing methods can be implemented.
LAN REDUNDANCY

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1.1.2.4 Expanding the Access Layer
Implementing Wireless Connectivity
The network must be designed to be able to expand network access to individuals and devices,
as needed. An increasingly important aspect of extending access layer connectivity is through
wireless connectivity. Providing wireless connectivity offers many advantages, such as
increased flexibility, reduced costs, and the ability to grow and adapt to changing network and
business requirements.
To communicate wirelessly, end devices require a wireless NIC that incorporates a radio
transmitter/receiver and the required software driver to make it operational. Additionally, a
wireless router or a wireless access point (AP) is required for users to connect.
There are many considerations when implementing a wireless network, such as the types of
wireless devices to use, wireless coverage requirements, interference considerations, and
security considerations.
1.1.2.5 Fine-tuning Routing Protocols
Managing the Routed Network
Enterprise networks and ISPs often use more advanced protocols, such as link-state protocols,
because of their hierarchical design and ability to scale for large networks.
Link-state routing protocols such as Open Shortest Path First (OSPF), works well for larger
hierarchical networks where fast convergence is important. OSPF routers establish and
maintain neighbor adjacency or adjacencies, with other connected OSPF routers. When routers
initiate an adjacency with neighbors, an exchange of link-state updates begins. Routers reach a
FULL state of adjacency when they have synchronized views on their link-state database. With
OSPF, link state updates are sent when network changes occur.
OSPF is a popular link-state routing protocol that can be fine-tuned in many ways.
Additionally, OSPF supports a two-layer hierarchical design, or multiarea OSPF. All OSPF
networks begin with Area 0, also called the backbone area. As the network is expanded, other,
non-backbone areas can be created. All non-backbone areas must directly connect to area 0.
Another popular routing protocol for larger networks is Enhanced Interior Gateway Routing
Protocol (EIGRP). Cisco developed EIGRP as a proprietary distance vector routing protocol with
enhanced capabilities. Although configuring EIGRP is relatively simple, the underlying features
and options of EIGRP are extensive and robust. For example, EIGRP uses multiple tables to
manage the routing process. EIGRP contains many features that are not found in any other
routing protocols. It is an excellent choice for large, multi-protocol networks that employ
primarily Cisco devices.

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1.1.2.6 Activity: Identify Scalability Terminology
1.2 Selecting Network Devices
1.2.1 Switch Hardware
1.2.1.1 Switch Platforms
When designing a network, it is important to select the proper hardware to meet current network
requirements, as well as allow for network growth. Within an enterprise network, both switches
and routers play a critical role in network communication.
There are five categories of switches for enterprise networks:
 Campus LAN Switches - To scale network performance in an enterprise LAN, there are
core, distribution, access, and compact switches. These switch platforms vary from
fanless switches with eight fixed ports to 13-blade switches supporting hundreds of
ports. Campus LAN switch platforms include the Cisco 2960, 3560, 3750, 3850, 4500,
6500, and 6800 Series.
 Cloud-Managed Switches - The Cisco Meraki cloud-managed access switches enable
virtual stacking of switches. They monitor and configure thousands of switch ports over
the web, without the intervention of onsite IT staff.
 Data Center Switches - A data center should be built based on switches that promote
infrastructure scalability, operational continuity, and transport flexibility. The data center
switch platforms include the Cisco Nexus Series switches and the Cisco Catalyst 6500
Series switches.
 Service Provider Switches - Service provider switches fall under two categories:
aggregation switches and Ethernet access switches. Aggregation switches are carrier-
grade Ethernet switches that aggregate traffic at the edge of a network. Service provider
Ethernet access switches feature application intelligence, unified services, virtualization,
integrated security, and simplified management.
 Virtual Networking - Networks are becoming increasingly virtualized. Cisco Nexus
virtual networking switch platforms provide secure multi-tenant services by adding
virtualization intelligence technology to the data center network.
When selecting switches, network administrators must determine the switch form factors. This
includes fixed configuration, modular configuration, stackable, or non-stackable. The thickness
of the switch, which is expressed in the number of rack units, is also important for switches that
are mounted in a rack.

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1.2.1.2 Port Density
The port density of a switch refers to the number of ports available on a single switch.
Fixed configuration switches typically support up to 48 ports on a single device. They have
options for up to four additional ports for small form-factor pluggable (SFP) devices. High-port
densities allow for better use of limited space and power. If there are two switches that each
contain 24 ports, they would be able to support up to 46 devices, because at least one port per
switch is lost with the connection of each switch to the rest of the network. In addition, two
power outlets are required. Alternatively, if there is a single 48-port switch, 47 devices can be
supported, with only one port used to connect the switch to the rest of the network, and only one
power outlet needed to accommodate the single switch.
Modular switches can support very high-port densities through the addition of multiple switch
port line cards. For example, some Catalyst 6500 switches can support in excess of 1,000
switch ports.
Large enterprise networks that support many thousands of network devices require high
density, modular switches to make the best use of space and power. Without using a high-
density modular switch, the network would need many fixed configuration switches to
accommodate the number of devices that need network access. This approach can consume
many power outlets and a lot of closet space.
The network designer must also consider the issue of uplink bottlenecks: A series of fixed
configuration switches may consume many additional ports for bandwidth aggregation between
switches, for the purpose of achieving target performance. With a single modular switch,
bandwidth aggregation is less of an issue, because the backplane of the chassis can provide
the necessary bandwidth to accommodate the devices connected to the switch port line cards.

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1.2.1.3 Forwarding Rates
Forwarding rates define the processing capabilities of a switch by rating how much data the
switch can process per second. Switch product lines are classified by forwarding rates, as
shown in the figure. Entry-level switches have lower forwarding rates than enterprise-level
switches. Forwarding rates are important to consider when selecting a switch. If the switch
forwarding rate is too low, it cannot accommodate full wire-speed communication across all of
its switch ports. Wire speed is the data rate that each Ethernet port on the switch is capable of
attaining. Data rates can be 100 Mb/s, 1 Gb/s, 10 Gb/s, or 100 Gb/s.
For example, a typical 48-port gigabit switch operating at full wire speed generates 48 Gb/s of
traffic. If the switch only supports a forwarding rate of 32 Gb/s, it cannot run at full wire speed
across all ports simultaneously. Fortunately, access layer switches typically do not need to
operate at full wire speed, because they are physically limited by their uplinks to the distribution
layer. This means that less expensive, lower performing switches can be used at the access
layer, and more expensive, higher performing switches can be used at the distribution and core
layers, where the forwarding rate has a greater impact on network performance.
1.2.1.4 Power over Ethernet
PoE allows the switch to deliver power to a device over the existing Ethernet cabling. This
feature can be used by IP phones and some wireless access points.
PoE allows more flexibility when installing wireless access points and IP phones, allowing them
to be installed anywhere that there is an Ethernet cable. A network administrator should ensure
that the PoE features are required, because switches that support PoE are expensive.
The relatively new Cisco Catalyst 2960-C and 3560-C Series compact switches support PoE
pass-through. PoE pass-through allows a network administrator to power PoE devices
connected to the switch, as well as the switch itself, by drawing power from certain upstream
switches.
1.2.1.5 Multilayer Switching
Multilayer switches are typically deployed in the core and distribution layers of an organization's
switched network. Multilayer switches are characterized by their ability to build a routing table,
support a few routing protocols, and forward IP packets at a rate close to that of Layer 2
forwarding. Multilayer switches often support specialized hardware, such as application-specific
integrated circuits (ASICs). ASICs along with dedicated software data structures can streamline
the forwarding of IP packets independent of the CPU.
There is a trend in networking toward a pure Layer 3 switched environment. When switches
were first used in networks, none of them supported routing; now, almost all switches support
routing. It is likely that soon all switches will incorporate a route processor because the cost of
doing so is decreasing relative to other constraints. Eventually the term multilayer switch will be
redundant.
The Catalyst 2960 switches illustrate the migration to a pure Layer 3 environment. With IOS
versions prior to 15.x, these switches supported only one active switched virtual interface (SVI).
With IOS 15.x, these switches now support multiple active SVIs. This means that the switch can
be remotely accessed via multiple IP addresses on distinct networks.

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1.2.1.6 Activity: Selecting Switch Hardware
1.2.2 Router Hardware
1.2.2.1 Router Requirements
In the distribution layer of an enterprise network, routing is required. Without the routing
process, packets cannot leave the local network.
Routers play a critical role in networking by interconnecting multiple sites within an enterprise
network, providing redundant paths, and connecting ISPs on the Internet. Routers can also act
as a translator between different media types and protocols. For example, a router can accept
packets from an Ethernet network and re-encapsulate them for transport over a Serial network.
Routers use the network portion of the destination IP address to route packets to the proper
destination. They select an alternate path if a link goes down or traffic is congested. All hosts on
a local network specify the IP address of the local router interface in their IP configuration. This
router interface is the default gateway.
Routers also serve other beneficial functions:
 Provide broadcast containment
 Connect remote locations
 Group users logically by application or department
 Provide enhanced security
With the enterprise and the ISP, the ability to route efficiently and recover from network link
failures is critical to delivering packets to their destination.

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1.2.2.2 Cisco Routers
As the network grows, it is important to select the proper routers to meet its requirements. There
are three categories of routers:
 Branch Routers - Branch routers optimize branch services on a single platform while
delivering an optimal application experience across branch and WAN infrastructures.
Maximizing service availability at the branch requires networks designed for 24x7x365
uptime. Highly available branch networks must ensure fast recovery from typical faults,
while minimizing or eliminating the impact on service, and provide simple network
configuration and management.
 Network Edge Routers - Network edge routers enable the network edge to deliver high-
performance, highly secure, and reliable services that unite campus, data center, and
branch networks. Customers expect a high-quality media experience and more types of
content than ever before. Customers want interactivity, personalization, mobility, and
control for all content. Customers also want to access content anytime and anyplace
they choose, over any device, whether at home, at work, or on the go. Network edge
routers must deliver enhance quality of service and nonstop video and mobile
capabilities.
 Service Provider Routers - Service provider routers differentiate the service portfolio
and increase revenues by delivering end-to-end scalable solutions and subscriber-aware
services. Operators must optimize operations, reduce expenses, and improve scalability
and flexibility, to deliver next-generation Internet experiences across all devices and
locations. These systems are designed to simplify and enhance the operation and
deployment of service-delivery networks.
1.2.2.3 Router Hardware
Routers also come in many form factors. Network administrators in an enterprise environment
should be able to support a variety of routers, from a small desktop router to a rack-mounted or
blade model.
Routers can also be categorized as fixed configuration or modular. With the fixed configuration,
the desired router interfaces are built-in. Modular routers come with multiple slots that allow a
network administrator to change the interfaces on the router. As an example, a Cisco 1841
router comes with two Fast Ethernet RJ-45 interfaces built-in, and two slots that can
accommodate many different network interface modules. Routers come with a variety of
different interfaces, such as Fast Ethernet, Gigabit Ethernet, Serial, and Fiber-Optic.

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1.2.2.4 Activity: Identify the Router Category

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1.2.3 Managing Devices
1.2.3.1 Managing IOS Files and Licensing
With such a wide selection of network devices to choose from in the Cisco product line, an
organization can carefully determine the ideal combination to meet the needs of the employees
and the customers.
When selecting or upgrading a Cisco IOS device, it is important to choose the proper IOS image
with the correct feature set and version. IOS refers to the package of routing, switching,
security, and other internetworking technologies integrated into a single multitasking operating
system. When a new device is shipped, it comes preinstalled with the software image and the
corresponding permanent licenses for the customer-specified packages and features.
For routers, beginning with Cisco IOS Software release 15.0, Cisco modified the process to
enable new technologies within the IOS feature sets.
1.2.3.2 In-band versus Out-of-band Management
Regardless of the Cisco IOS network device being implemented, there are two methods for
connecting a PC to that network device for configuration and monitoring tasks. These methods
include out-of-band and in-band management.
Out-of-band management is used for initial configuration or when a network connection is
unavailable. Configuration using out-of-band management requires:
 Direct connection to console or AUX port
 Terminal emulation client
In-band management is used to monitor and make configuration changes to a network device
over a network connection. Configuration using in-band management requires:
 At least one network interface on the device to be connected and operational
 Telnet, SSH, or HTTP to access a Cisco device

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1.2.3.3 Basic Router CLI Commands
A basic router configuration includes the hostname for identification, passwords for security,
assignment of IP addresses to interfaces for connectivity, and basic routing. Verify and save
configuration changes using the copy running-config startup-config command. To clear the
router configuration, use the erase startup-config command and then the reload command.
Enable a Router with OSPF
Router# configure terminal
Router (config)# hostname R1
R1 (config)# enable secret class
R1 (config)# line console 0
R1 (config-line)# password cisco
R1 (config-line)# login
R1 (config-line)# exec-timeout 0 0
R1 (config-line)# line vty 0 4
R1 (config-line)# password cisco
R1 (config-line)# login
R1 (config-line)# exit
R1 (config)# service password-encryption
R1 (config)# banner motd $ Authorized Access Only! $
R1 (config)# interface GigabitEthernet0/0
R1 (config-if)# description Link to LAN 1
R1 (config-if)# ip address 172.16.1.1 255.255.255.0
R1 (config-if)# no shutdown
R1 (config-if)# interface Serial0/0/0
R1 (config-if)# descritption Link to R2
R1 (config-if)# clock rate 128000
R1 (config-if)# interface Serial0/0/1
R1 (config-if)# descritpion Link to R3
R1 (config-if)# exit
R1 (config)# router ospf 10
R1 (config-router)# router-id 1.1.1.1
R1 (config-router)# network 172.16.1.0 0.0.0.255 area 0
R1 (config-router)# exit
R1 (config)# end
By running the command:
R1 # show running-config
This will show the results of the
configuration commands that were
entered on the left side.

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1.2.3.4 Basic Router Show Commands
Here are some of the most commonly used IOS commands to display and verify the operational
status of the router and related network functionality. These commands are divided into several
categories.
Routing Related:
 show ip protocols - Displays information about the routing protocols configured. If
OSPF is configured, this includes the OSPF process ID, the router ID, networks the
router is advertising, the neighbors the router is receiving updates from, and the default
administrative distance, which is 110 for OSPF.
 show ip route - Displays routing table information, including: routing codes, known
networks, administrative distance and metrics, how routes were learned, next hop, static
routes, and default routes.
 show ip ospf neighbor - Displays information about OSPF neighbors that have been
learned, including the Router ID of the neighbor, priority, the state (Full = adjacency has
been formed), the IP address, and the local interface that learned of the neighbor.
Interface Related:
 show interfaces - Displays interfaces with line (protocol) status, bandwidth, delay,
reliability, encapsulation, duplex, and I/O statistics. If specified without a specific
interface designation, all interfaces will be displayed. If a specific interface is specified
after the command, information about that interface only will be displayed.
 show ip interfaces - Displays interface information, including: protocol status, the IP
address, if a helper address is configured, and whether an ACL is enabled on the
interface. If specified without a specific interface designation, all interfaces will be
displayed. If a specific interface is specified after the command, information about that
interface only will be displayed.
 show ip interface brief - Displays all interfaces with IP addressing information and
interface and line protocols status.
 show protocols - Displays information about the routed protocol that is enabled, and
the protocol status of interfaces.
Other connectivity related commands include the show cdp neighbors command. This
command displays information on directly connected devices including Device ID, the local
interface the device is connected to, capability (R = router, S = switch), the platform, and Port ID
of the remote device. The details option includes IP addressing information and the IOS version.

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1.2.3.5 Basic Switch CLI Commands
Basic switch configuration includes the hostname for identification, passwords for security, and
assignment of IP addresses for connectivity. In-band access requires the switch to have an IP
address.
To verify and save the switch configuration using the copy running-config startup-config
command. To clear the switch configuration, use the erase startup-config command and then
the reload command. It may also be necessary to erase any VLAN information using the
command delete flash:vlan.dat. When switch configurations are in place, view the
configurations using the show running-config command.
Switch# enable
Switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch (config)# hostname S1
S1 (config)# banner motd %Unauthorized access prohibited%
S1 (config)# enable password cisco
S1 (config)# enable secret class
S1 (config)# line console 0
S1 (config-line)# password cisco
S1 (config-line)# login
S1 (config-line)# line vty 0 4
S1 (config-line)# password cisco
S1 (config-line)# login
S1 (config-line)# interface vlan 1
S1 (config-if)# ip address 192.168.1.5 255.255.255.0
S1 (config-if)# no shutdown
S1 (config-if)# exit
S1 (config)# ip default-gateway 192.168.1.1
S1 (config)# interface fa0/2
S1 (config-if)# switchport mode access
S1 (config-if)# switchport port-security
S1 (config-if)# end
S1#
S1# copy running-config startup-config
Destination filename [startup/config]?
Building configuration...
[OK]
S1#
By running the command:
S1 # show running-config
This will show the results of the
configuration commands that were
entered on the left side.

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1.2.3.6 Basic Switch Show Commands
Switches make use of common IOS commands for configuration, to check for connectivity and
to display current switch status.
Interface / Port Related:
 show port-security - Displays any ports with security activated. To examine a specific
interface, include the interface ID. Information included in the output: the maximum
addresses allowed, current count, security violation count, and action to be taken.
 show port-security address - Displays all secure MAC addresses configured on all
switch interfaces.
 show interfaces - Displays one or all interfaces with line (protocol) status, bandwidth,
delay, reliability, encapsulation, duplex, and I/O statistics.
 show mac-address-table - Displays all MAC addresses that the switch has learned,
how those addresses were learned (dynamic/static), the port number, and the VLAN
assigned to the port.
Like the router, the switch also supports the show cdp neighbors command.
The same in-band and out-of-band management techniques that apply to routers also applies to
switch configuration.
1.3 Summary
1.3.1 Summary
1.3.1.4 Summary
The hierarchical network design model divides network functionality into the access layer, the
distribution layer, and the core layer. The Cisco Enterprise Architecture further divides the
network into functional components.
A well-designed network controls traffic and limits the size of failure domains. Routers and
multilayer switches can be deployed in pairs so that the failure of a single device does not cause
service disruptions.
A network design should include an IP addressing strategy, scalable, and fast-converging
routing protocols, appropriate Layer 2 protocols, and modular or clustered devices that can be
easily upgraded to increase capacity.
A mission-critical server should have a connection to two different access layer switches. It
should have redundant modules when possible, and a power backup source. It may be
appropriate to provide multiple connections to one or more ISPs.
Security monitoring systems and IP telephony systems must have high availability and often
have special design considerations.
The network designer should specify a router from the appropriate category: branch router,
network edge router, or service provider router. It is important to also deploy the appropriate
type of switches for a given set of requirements, switch features and specifications, and
expected traffic flow.

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