1. 2 cisco ios cisco technology is built around the cisco internetwork operating system (ios), which...

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Cisco IOS

Cisco technology is built around the Cisco Internetwork Operating System (IOS), which is the software that controls the routing and switching functions of internetworking devices.

A solid understanding of the IOS is essential for a network administrator.

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The Purpose of Cisco IOS

As with a computer, a router or switch cannot function without an operating system. Cisco calls its operating system the Cisco Internetwork Operating System or Cisco IOS.

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Introduction to Routers

A router is a special type of computer. It has the same basic components as a standard desktop PC. However, routers are designed to perform some very specific functions. Just as computers need operating systems to run software applications, routers need the Internetwork Operating System software (IOS) to run configuration files. These configuration files contain the instructions and parameters that control the flow of traffic in and out of the routers. The many parts of a router are shown below:

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Router Memory Components

ROM - Read Only Memory – Bootstrap/POST

FLASH Memory- IOS Images are kept here- Erasable reprogrammable ROM- Contents are kept on Power down or

reload

RAM - Random Access memory- Routing Tables- Running Configuration- Contents are lost on reboot

NVRAM - Start up configuration- Configuration Register- Contents are kept on reload

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ROM

Read-Only Memory

ROM has the following characteristics and functions:

Maintains instructions for power-on self test (POST) diagnostics Stores bootstrap program and basic operating system software Mini IOS

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RAM

Random Access Memory, also called dynamic RAM (DRAM)

RAM has the following characteristics and functions:

Stores routing tables Holds ARP cache Performs packet buffering (shared RAM) Provides temporary memory for the configuration file of the router while the router is powered on Loses content when router is powered down or restarted

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NVRAM

Non-Volatile RAM

NVRAM has the following characteristics and functions:

Provides storage for the startup configuration file Retains content when router is powered down or restarted Configuration Register – 16 bit register which decides boot sequence

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Flash

Flash memory has the following characteristics and functions:

Holds the operating system image (IOS) Allows software to be updated without removing and replacing chips on the processor Retains content when router is powered down or restarted Can store multiple versions of IOS software Is a type of electronically erasable, programmable ROM (EEPROM)

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InterfacesInterfaces have the following characteristics and functions:

Connect router to network for frame entry and exit

Can be on the motherboard or on a separate module

Types of interfaces:

Ethernet Fast Ethernet Serial ISDN BRI Loopback Console Aux

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Router Internal Components

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Router Power-On/Bootup Sequence

1. Perform power-on self test (POST).2. Load and run bootstrap code.3. Find the Cisco IOS software.4. Load the Cisco IOS software.5. Find the configuration.6. Load the configuration.7. Run the configured Cisco IOS

software.

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Boot Sequence

ROMMonitor

RXBootFLASH

Configuration Register

C-FileNVRAM

Y

N

Running

Setup Mode

Checks All interfaces

RAM

1415 13 12 1011 9 8 67 5 4 23 1 0

48 2 1 48 2 1 48 2 1 48 2 1

0 0 0 0

0 0 0 1

0 0 1 0

ROMMonitorRxBootFlash

1 1 1 1

0

1

2-15

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After the Post…

After the POST, the following events occur as the router initializes:

Step 1The generic bootstrap loader in ROM executes. A bootstrap is a simple set of instructions that tests hardware and initializes the IOS for operation. 

Step 2The IOS can be found in several places. The boot field of the configuration register determines the location to be used in loading the IOS.

Step 3The operating system image is loaded.

Step 4The configuration file saved in NVRAM is loaded into main memory and executed one line at a time. The configuration commands start routing processes, supply addresses for interfaces, and define other operating characteristics of the router.

Step 5If no valid configuration file exists in NVRAM, the operating system searches for an available TFTP server. If no TFTP server is found, the setup dialog is initiated.  

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Loading the Cisco IOS Software From Flash Memory

• The flash memory file is decompressed into RAM.

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Loading the Configuration

• Load and execute the configuration from NVRAM.

• If no configuration is present in NVRAM, enter setup mode.

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External Components of a 2600 Router

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Internal Components of a 2600 Router

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Computer/Terminal Console Connection

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HyperTerminal Session Properties

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Establishing aHyperTerminal Session

Take the following steps to connect a terminal to the console port on the router:

First, connect the terminal using the RJ-45 to RJ-45 rollover cable and an RJ-45 to DB-9 or RJ-45 to DB-25 adapter.

Then, configure the terminal or PC terminal emulation software for 9600 baud, 8 data bits, no parity, 1 stop bit, and no flow control.

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Router Command Line Interface

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IOS File System Overview

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Router LED Indicators

Cisco routers use LED indicators to provide status information. Depending upon the Cisco router model, the LED indicators will vary. An interface LED indicates the activity of the corresponding interface. If an LED is off when the interface is active and the interface is correctly connected, a problem may be indicated. If an interface is extremely busy, its LED will always be on. The green OK LED to the right of the AUX port will be on after the system initializes correctly.

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Router User Interface Modes

The Cisco command-line interface (CLI) uses a hierarchical structure. This structure requires entry into different modes to accomplish particular tasks.

Each configuration mode is indicated with a distinctive prompt and allows only commands that are appropriate for that mode.

As a security feature the Cisco IOS software separates sessions into two access levels, user EXEC mode and privileged EXEC mode. The privileged EXEC mode is also known as enable mode.

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Overview of Router Modes

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Router Modes

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CLI Command Modes

All command-line interface (CLI) configuration changes to a Cisco router are made from the global configuration mode. Other more specific modes are entered depending upon the configuration change that is required.

Global configuration mode commands are used in a router to apply configuration statements that affect the system as a whole.

The following command moves the router into global configuration mode

Router#configure terminal (or config t)Router(config)#

When specific configuration modes are entered, the router prompt changes to indicate the current configuration mode.

Typing exit from one of these specific configuration modes will return the router to global configuration mode. Pressing Ctrl-Z returns the router to all the way back privileged EXEC mode.

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Show Version Command

wg_ro_a#show versionCisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JS-L), Version 12.0(3), RELEASE SOFTWARE (fc1)Copyright (c) 1986-1999 by cisco Systems, Inc.Compiled Mon 08-Feb-99 18:18 by phanguyeImage text-base: 0x03050C84, data-base: 0x00001000

ROM: System Bootstrap, Version 11.0(10c), SOFTWAREBOOTFLASH: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE(fc1)

wg_ro_a uptime is 20 minutesSystem restarted by reloadSystem image file is "flash:c2500-js-l_120-3.bin"(output omitted)--More--

Configuration register is 0x2102

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Viewing the Configuration

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show running-config and show startup-config

Commands

wg_ro_c#show startup-configUsing 1359 out of 32762 bytes!version 12.0!

-- More --

wg_ro_c#show running-configBuilding configuration...

Current configuration:!version 12.0!

-- More --

In NVRAMIn RAM

• Displays the current and saved configuration

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Configurations in two locations - RAM and NVRAM.

•The running configuration is stored in RAM. •Any configuration changes to the router are made to the running-configuration and take effect immediately after the command is entered. •The startup-configuration is saved in NVRAM and is loaded into the router's running-configuration when the router boots up. • To save the running-configuration to the startup configuration, type the following from privileged EXEC mode (i.e. at the "Router#" prompt.)

Router# copy run start

Saving Configurations

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Command Abbreviation

Show Configuration – sh confConfigure Terminal – conf tLine auxillary – line auxLine console – line con

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Configuring a Router’s Name

A router should be given a unique name as one of the first configuration tasks.

This task is accomplished in global configuration mode using the following commands:

Router(config)#hostname GatesGates(config)#

As soon as the Enter key is pressed, the prompt changes from the default host name (Router) to the newly configured host name (which is Gates in the example above).

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Settingthe Clockwith Help

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Message Of The Day (MOTD)

A message-of-the-day (MOTD) banner can be displayed on all connected terminals.

Enter global configuration mode by using the command config t

Enter the commandbanner motd # Welcome to Gates Training #.

Save changes by issuing the command copy run start

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Privileged Mode Command

# show startup-config# show running-config# show version# show flash# show interfaces# show interfaces s 0# show history# show terminal# terminal history size 25

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Password

Passwords restrict access to routers. Passwords should always be configured for virtual terminal lines and the console line. Passwords are also used to control access to privileged EXEC mode so that only authorized users may make changes to the configuration file.

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Passwords

There are five passwords for RouterPrivileged Mode Password – 2Line Console PasswordAuxiliary Port PasswordTelnet Password

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Privileged Mode Password

Gates(config)# enable password gatesEncrypted privilege mode passwordGates(config)# enable secret gates1

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Line Password

Gates(config)# line console 0Gates(config)# password ciscoGates(config)# login

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Aux Port Password

Gates(config)# line aux 0Gates(config)# password ciscoGates(config)# login

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Connecting to Aux Port

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Configuring a Telnet Password

A password must be set on one or more of the virtual terminal (VTY) lines for users to gain remote access to the router using Telnet.

Typically Cisco routers support five VTY lines numbered 0 through 4.

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Telnet Password

Gates(config)# line vty 0 4Gates(config)# password ciscoGates(config)# login

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Encrypting Passwords

Only the enable secret password is encrypted by default

Need to manually configure the user-mode and enable passwords for encryption

To manually encrypt your passwords, use the service password-encryption command

Router#config t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#service password-encryption

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Disable Passwords

Gates(config)# no enable passwordGates(config)# no enable secretFor the ConsoleGates(config)# line con 0Gates(config)# no passwordGates(config)# line vty 0 4Gates(config)# no password

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LAB – Interface Configuration

S0 S0E010.0.0.1

10.0.0.2

30.0.0.220.0.0.120.0.0.2 30.0.0.1

A

S0

E0

40.0.0.2

40.0.0.1

B

S1

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Descriptions

Setting descriptions on an interface is helpful to the administrator

Only locally significant R1(config)#int e0R1(config-if)#description Sales Lan

R1(config-if)#int s0

R1(config-if)#desc Wan to Mumbai

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Configuring Interfaces

An interface needs an IP Address and a Subnet Mask to be configured. All interfaces are “shutdown” by default. The DCE end of a serial interface needs a clock rate.R1#config tR1(config)#int e0R1(config)#Description Connoted to Host R1(config-if)#ip address 10.0.0.1 255.0.0.0R1(config-if)#no shutdownR1(config-if)#exitR1(config)#interface serial 0R1(config-if)#ip address 20.0.0.1 255.255.255.0R1(config-if)# bandwidth 64R1(config-if)#clock rate 64000 (required for serial DCE only) R1(config-if)#no shutdownR1(config-if)#exitR1(config)#exitR1#

On new routers, Serial 1 would be just Serial 0/1 and e0 would be f0/0.s = serial e = Ethernet f = fast Ethernet

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DCE DTE

To find out DCE or DTE#Show controllers s 0

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Viewing Configuration

To Check the status of interface#Show IP interface brief or#Sh IP int brief

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Saving and Erasing Configurations

To copy RAM to NVRAM

# copy run startup-config

To remove all configuration# erase startup-config# reload

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Objectives

Upon completion of this chapter, you will be able to complete the following tasks:Distinguish the use and operation of static and

dynamic routes

Configure and verify a static route

Identify how distance vector IP routing protocols such as RIP and IGRP operate on Cisco routers

Enable Routing Information Protocol (RIP)

Enable Interior Gateway Routing Protocol (IGRP)

Verify IP routing with show and debug commands

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Routing

The process of transferring data from one local area network to another

Layer 3 devicesRouted protocol Enables to forward packet from

one router to another – Ex – IP, IPXRouting protocol sends and receives routing

information packets to and from other routers – Ex -RIP, OSPF , IGRP

Routing protocols gather and share the routing information used to maintain and update routing tables.

That routing information is in turn used to route a routed protocol to its final destination

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Routing

FromRaj

House #213, 4th Street

Jayanagar, Bangalore

ToRam

House #452, 2nd Street

Dadar, Mumbai

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To route, a router needs to know:Destination addressesSources it can learn fromPossible routesBest route

What is Routing?

172.16.1.010.120.2.0

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What is Routing? (cont.)What is Routing? (cont.)

NetworkProtocol

DestinationNetwork

ConnectedLearned

10.120.2.0172.16.1.0

Exit Interface

E0S0

Routed Protocol: IP

Routers must learn destinations that are not directly connected

172.16.1.010.120.2.0

E0S0

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Route Types

Static routing - network administrator configures information about remote networks manually. They are used to reduce overhead and for security.

Dynamic routing - information is learned from other routers, and routing protocols adjust routes automatically.

Because of the extra administrative requirements, static routing does not have the scalability of dynamic routing.

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IP Routing Process

Step-by-step what happens when Host A wants to communicate with Host B on a different network

A user on Host A pings Host B’s IP address.

E0 E110.0.0.1

10.0.0.2A B 20.0.0.2

20.0.0.1

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LAB – Interface Configuration

S0 S0E010.0.0.1

10.0.0.2

30.0.0.220.0.0.120.0.0.2 30.0.0.1

A

S0

E0

40.0.0.2

40.0.0.1

B

S1

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Test The Connection

• Host A can ping router R1 and R2• To enable Host A to Ping Host B we need to

configure Routes

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IP Routing

The different types of routing are:Static routingDefault routingDynamic routing

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Static Routes

BenefitsNo overhead on the router CPU No bandwidth usage between routers Adds security

DisadvantageAdministrator must really understand the internetworkIf a network is added to the internetwork, the

administrator has to add a route to it on all routers Not feasible in large networks

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– R1(config)# iproute DestAddress SNM Nexthop address

R1(config)#ip route network [mask] {address | interface}[distance] [permanent]

Static Route Configuration

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ip route The command used to create the static route. destination_network The network you’re placing in the routing table. mask The subnet mask being used on the network. next-hop_address The address of the next-hop router that will receive

the packet and forward it to the remote network. This is a router interface that’s on a directly connected network.

exitinterface You can use it in place of the next-hop address if you want, but it’s got to be on a point-to-point link, such as a WAN

administrative_distance By default, static routes have an administrative distance of 1 (or even 0 if you use an exit interface instead of a next-hop address)

permanent If the interface is shut down, or the router can’t communicate to the next-hop router, the route will automatically be discarded from the routing table. Choosing the permanent option keeps the entry in the routing table no matter what happens.

ip route [destination_network] [mask] [next-hop_address or exitinterface] [administrative_distance] [permanent

Static Route ConfigurationStatic Route Configuration

R1(config)#ip route 30.0.0.0 255.0.0.0 20.0.0.2

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LAB – Static Route Configuration

S0 S0E010.0.0.1

10.0.0.2

30.0.0.220.0.0.120.0.0.2 30.0.0.1

A

S0

E0

40.0.0.2

40.0.0.1

B

S1

R1# config tR1(config)#ip route 30.0.0.0 255.0.0.0 20.0.0.2R1(config)#ip route 40.0.0.0 255.0.0.0 20.0.0.2

R2# config tR2(config)#ip route 10.0.0.0 255.0.0.0 20.0.0.1R2(config)#ip route 40.0.0.0 255.0.0.0 30.0.0.2

R3# config tR3(config)#ip route 10.0.0.0 255.0.0.0 30.0.0.1R3(config)#ip route 20.0.0.0 255.0.0.0 30.0.0.1

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Verifying StaticRoute Configuration

After static routes are configured it is important to verify that they are present in the routing table and that routing is working as expected.

The command show running-config is used to view the active configuration in RAM to verify that the static route was entered correctly.

The show ip route command is used to make sure that the static route is present in the routing table.

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S0 S0E010.0.0.1

10.0.0.2

30.0.0.220.0.0.120.0.0.2 30.0.0.1

A

S0

E0

40.0.0.2

40.0.0.1

B

S1

R1# config tR1(config)#no ip route 30.0.0.0 255.0.0.0 20.0.0.2R1(config)#no ip route 40.0.0.0 255.0.0.0 20.0.0.2

R2# config tR2(config)#no ip route 10.0.0.0 255.0.0.0 20.0.0.1R2(config)#no ip route 40.0.0.0 255.0.0.0 30.0.0.2

R3# config tR3(config)#no ip route 10.0.0.0 255.0.0.0 30.0.0.1R3(config)#no ip route 20.0.0.0 255.0.0.0 30.0.0.1

Removing IP Route

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Default Routes

• Can only use default routing on stub networks• Stub networks are those with only one exit path

out of the network• The only routers that are considered to be in a

stub network are R1 and R3

S0S0E0

E010.0.0.1

10.0.0.2 40.0.0.2

20.0.0.1

20.0.0.2

30.0.0.1

A B

S0S1

30.0.0.2

40.0.0.1

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Stub Network

ip route 0.0.0.0 0.0.0.0 172.16.2.2

Default Routes

172.16.2.1

SO

172.16.1.0

B172.16.2.2

NetworkA B

This route allows the stub network to reach all known networks beyond router A.

10.0.0.0

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Configuring Default Routes

Default routes are used to route packets with destinations that do not match any of the other routes in the routing table.

A default route is actually a special static route that uses this format:

ip route 0.0.0.0 0.0.0.0 [next-hop-address | outgoing interface]

This is sometimes referred to as a “Quad-Zero” route.

Example using next hop address:

Router(config)#ip route 0.0.0.0 0.0.0.0 172.16.4.1

Example using the exit interface:

Router(config)#ip route 0.0.0.0 0.0.0.0 s0/0

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S0S0E0

E010.0.0.1

10.0.0.2 40.0.0.2

20.0.0.1

20.0.0.2

30.0.0.1

A B

S0S1

30.0.0.2

40.0.0.1

LAB Configuration

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Default Route LAB Configuration

S0S0E0

E010.0.0.1

10.0.0.2 40.0.0.2

20.0.0.1

20.0.0.2

30.0.0.1

A B

S0S1

30.0.0.2

40.0.0.1

R1# config tR1(config)#ip route 0.0.0.0 0.0.0.0 20.0.0.2

R3# config tR3(config)#ip route 0.0.0.0 0.0.0.0 30.0.0.1

R2# config tR2(config)#ip route 10.0.0.0 255.0.0.0 20.0.0.1R2(config)#ip route 40.0.0.0 255.0.0.0 30.0.0.2

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What is a Routing Protocol?

What is a Routing Protocol?

Routing protocols are

used between routers to determine paths and maintain routing tables.

Once the path is determined a router can route a routed protocol.

NetworkProtocol

DestinationNetwork

ConnectedRIP

IGRP

10.120.2.0172.16.2.0172.17.3.0

Exit Interface

E0S0S1

Routed Protocol: IPRouting protocol: RIP, IGRP

172.17.3.0

172.16.1.010.120.2.0

E0S0

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Autonomous System

AS 2000

AS 3000

IGP

Interior Gateway Protocols areused for routing decisions

within an Autonomous System.

Exterior GatewayProtocols are usedfor routing between

Autonomous Systems

EGP

AS 1000

An Autonomous System (AS) is a group of IP networks, which has a single and clearly defined routing policy. Group of routers which can exchange updatesAS are identified by numbers

Fig. 48 IGP and EGP (TI1332EU02TI_0004 The Network Layer, 67)

All Routing protocols are categorized as IGP or EGP

Routing CategoriesRouting Categories

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IGP

Interior Gateway Protocol(IGP)

Exterior Gateway Protocol (EGP)

EGP

EGP

EGP

Interior Gateway Protocol(IGP)

AS 1000

AS 2000

AS 3000

Fig. 49 The use of IGP and EGP protocols (TI1332EU02TI_0004 The Network Layer, 67)

Routing CategoriesRouting Categories

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An autonomous system is a collection of networks under a common administrative domain.

IGPs operate within an autonomous system.

EGPs connect different autonomous systems.

Autonomous Systems: Interior or Exterior Routing Protocols

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Types or Classes of Routing Protocols

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Distance VectorRIP V1IGRPRIP V2

Link stateOSPF

HybridEIGRP

Types or Classes of Routing Protocols

86

Classful Routing Overview

Classful routing protocols do not include the subnet mask with the route advertisement.

Within the same network, consistency of the subnet masks is assumed.

Summary routes are exchanged between foreign networks.

Examples of classful routing protocols:RIP Version 1 (RIPv1)IGRP

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Classless Routing Overview

Classless routing protocols include the subnet mask with the route advertisement.

Classless routing protocols support variable-length subnet masking (VLSM) and subnetting

Examples of classless routing protocols:RIP Version 2 (RIPv2)EIGRPOSPFIS-IS

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• Routers pass periodic copies of routing table to neighbor routers and accumulate distance vectors.

Distance Vector Routing Protocols

89

Distance Vector

Uses Bellman Ford Algorithm It needs to find out the shortest path from one network to other How to determine which path is best?

192.168.10.1192.168.20.1

90

Distance Vector

There are two Distance Vector Protocol, Both uses different metric RIP – Hops IGRP - Composite

192.168.10.1

192.168.20.1

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Distance Vector

DV protocol are known as Routing by rumor RIP uses only Hop count RI routing table metric for 192.168.20.1 network will be

3 2

192.168.10.1

192.168.20.1

0

1

1

2

2

3R1

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Distance Vector

192.168.10.1

192.168.20.1

56 kbps

1 Mbps1 Mbps

1 Mbps

56 kbps

• IGGRP uses bandwidth and delay as Metric• RI routing table metric for 192.168.20.1 network will be

– 30– 60

R110

10

10

30 30192.168.10.1

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Routing Loops

A network problem in which packets continue to be routed in an endless circle

94

• Routers discover the best path to destinations from each neighbor.

Sources of Information and Discovering Routes

95

• Each node maintains the distance from itself to each possible destination network.

Inconsistent Routing Entries

96

• Slow convergence produces inconsistent routing.

Inconsistent Routing Entries (Cont.)

97

• Router C concludes that the best path to network 10.4.0.0 is through router B.

Inconsistent Routing Entries (Cont.)

98

• Router A updates its table to reflect the new but erroneous hop count.

Inconsistent Routing Entries (Cont.)

99

Hop count for network 10.4.0.0 counts to infinity.

Count to Infinity

100

• Packets for network 10.4.0.0 bounce (loop) between routers B and C.

Routing Loops

101

• Define a limit on the number of hops to prevent infinite loops.

Defining a Maximum

102

Maximum Hop Count

• One way of solving routing loop problem is to define a maximum hop count.

• RIP permits a hop count of up to 15, so anything that requires 16 hops is deemed unreachable

• The maximum hop count will control how long it takes for a routing table entry to become invalid

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• It is never useful to send information about a route back in the direction from which the original information came.

Split Horizon

104

Split Horizon

Solution to the Routing Loop problemSplit Horizon is a rule that routing

information cannot be sent back in the direction from which it was received

Had split horizon been used in our example, Router B would not have included information about network 10.4.0.0 in its update to Router C.

105

Route Poisoning

• Route Poisoning. Usually used in conjunction with split horizon

• Route poisoning involves explicitly poisoning a routing table entry for an unreachable network

• Once Router C learned that network 10.4.0.0 was unavailable it would have immediately poisoned the route to that network by setting its hop count to the routing protocol’s infinity value

• In the case of RIP, that would mean a hop count

of 16.

106

Triggered Updates

New routing tables are sent to neighboring routers on a regular basis.

RIP updates occur every 30 seconds

However a triggered update is sent immediately in response to some change in the routing table.

The router that detects a topology change immediately sends an update message to adjacent routers that, in turn, generate triggered updates notifying their adjacent neighbors of the change.

Triggered updates, used in conjunction with route poisoning, ensure that all routers know of failed routes.

107

Triggered Updates Graphic

108

Holddowns

• Holddowns are a technique used to ensure that a route recently removed or changed is not reinstated by a routing table update from another route

• Holddown prevents regular update messages from reinstating a route that is going up and down (called flapping)

• Holddowns prevent routes from changing too rapidly by allowing time for either the downed route to come back up

• Holddowns make a router wait a period of time before accepting an update for a network whose status or metric has recently changed

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Solution: Holddown Timers

110

Pinhole Congestion

192.168.10.1

192.168.20.1

1Mbps 1Mbps

56kbps56kbps

111

RIP Timers

• Route update timer Sets the interval (typically 30 seconds) between periodic routing updates

• Route invalid timer Determines the length of time (180 seconds) before a router determines that a route has become invalid

• Holddown timer This sets the amount of time during which routing information is suppressed. This continues until either an update packet is received with a better metric or until the holddown timer expires. The default is 180 seconds

• Route flush timer Sets the time between a route becoming invalid and its removal from the routing table (240 seconds).

112

Routing Information Protocol (RIP)

Routing Information Protocol (RIP) is a true distance-vector routing protocol.

It sends the complete routing table out to all active interfaces every 30 seconds

RIP only uses hop count to determine the best way to a remote network

It has a maximum allowable hop count of 15 AD is 120 Bellman-ford algorithm Works well in small networks, but it’s inefficient on large

networks RIP version 1 uses only classful routing, which means that

all devices in the network must use the same subnet mask RIP version 2 does send subnet mask information with the

route updates. This is called classless routing.

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Router Configuration

The router command starts a routing process.

The network command is required because it enables the routing process to determine which interfaces participate in the sending and receiving of routing updates.

An example of a routing configuration is:

Gates(config)#router ripGates(config-router)#network 172.16.0.0

The network numbers are based on the network class addresses, not subnet addresses or individual host addresses.

114

RIP Configuration

S0S0

E0E0

192.168.10.1

A B

S0S1

R1# config tR1(config)# )#router ripR1(config)#network 192.168.10.0R1(config)#network 192.168.20.0

R2# config tR2(config)#router ripR2(config)#network 192.168.20.0R2(config)#network 192.168.30.0192.168.10.2

192.168.20.1

192.168.20.2

192.168.30.1

192.168.30.2 192.168.40.1

192.168.40.2

R3# config tR3(config)# )#router ripR3(config)#network 192.168.30.0R3(config)#network 192.168.40.0

115

Verifying RIP Configuration

116

Displaying the IP Routing Table

117

debug ip rip Command

118

Passive Interface

Passive-interface command prevents RIP update broadcasts from being sent out a defined interface, but same interface can still receive RIP updates

R1#config tR1(config)#router ripR1(config-router)#network 192.168.10.0R1(config-router)#passive-interface serial 0

Passive-interface command depends upon the routing protocol

RIP router with a passive interface will still learn about the networks advertised by other routers

EIGRP, a passive-interface will neither send nor receive updates.

119

RIP Version 2 (RIPv2)

R1# config tR1(config)# )#router ripR1(config)#network 192.168.10.0R1(config)#network 192.168.20.0R1(config)#version 2

120

Exercise - RIP Version 2 Configuration

S0S0

E0E0

192.168.0.16/29

A B

S0S1

192.168.0.4/30 192.168.0.8/30

192.168.0.32/28

1. Find out the IP Address and SNM of each interfaces

121

Exercise - RIP Version 2 Configuration

S0S0

E0E0

192.168.0.18255.255.255.248

A B

S0S1

192.168.0.17255.255.255.248

192.168.0.5255.255.255.252

192.168.0.6255.255.255.252

192.168.0.9255.255.255.252

192.168.0.10255.255.255.252

192.168.0.33255.255.255.240

192.168.0.34255.255.255.240

122

Exercise - RIP Version 2 Configuration

S0S0

E0E0

192.168.0.16/29

A B

S0S1

192.168.0.4/30 192.168.0.8/30

192.168.0.32/28R2# config tR2(config)#router ripR2(config)#network 192.168.0.4R2(config)#network 192.168.0.8R2(config)#version 2

R1# config tR1(config)# )#router ripR1(config)#network 192.168.0.4R1(config)#network 192.168.0.16R1(config)#version 2

R3# config tR3(config)# )#router ripR3(config)#network 192.168.0.8R3(config)#network 192.168.0.32R3(config)#version 2

123© 2002, Cisco Systems, Inc. All rights reserved. 123

Enabling IGRP

124

CISCO ProprietaryMore scalable than RIPSophisticated metric

Introducing IGRP

125

BandwidthDelayReliabilityLoadMTU

IGRP Composite Metric

126

IGRP

Some of the IGRP key design characteristics emphasize the following:

It is a distance vector routing protocol.

Routing updates are broadcast every 90 seconds.

Bandwidth, load, delay and reliability are used to create

a composite metric. The main difference between RIP and IGRP

configuration is that when you configure IGRP, you supply the autonomous system number. All routers must use the same number in order to share routing table information.

127

IGRP Vs RIP

129

Configuring IGRP

130

IGRP Configuration

S0S0

E0E0

192.168.10.1

A B

S0S1

R1# config tR1(config)# )#router igrp 10R1(config)#network 192.168.10.0R1(config)#network 192.168.20.0

R2# config tR2(config)#router igrp 10R2(config)#network 192.168.20.0R2(config)#network 192.168.30.0192.168.10.2

192.168.20.1

192.168.20.2

192.168.30.1

192.168.30.2 192.168.40.1

192.168.40.2

R3# config tR3(config)# )#router igrp 10R3(config)#network 192.168.30.0R3(config)#network 192.168.40.0

131

Verifying the IGRP Routing Tables

LabA#sh ip route[output cut]I 192.168.50.0 [100/170420] via 192.168.20.2, Serial0/0I 192.168.40.0 [100/160260] via 192.168.20.2, Serial0/0I 192.168.30.0 [100/158360] via 192.168.20.2, Serial0/0C 192.168.20.0 is directly connected Serial0/0C 192.168.10.0 is directly connected, FastEthernet0/0• The I means IGRP-injected routes. The 100 in [100/160360]

is the administrative distance of IGRP. The 160,360 is the composite metric. The lower the composite metric, the better the route.

• To delete all routesclear ip route

132

Debug Commands

debug ip igrp events Command summary of the IGRP routing information that is running

on the network.

debug ip igrp transactions Command shows message requests from neighbor routers asking

for an update and the broadcasts sent from your router toward that neighbor router.

no debug all – to turn off all debug