CCNA

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.
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.


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:
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

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
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
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
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)
Interfaces
Interfaces 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
Router Internal Components
Router Power-On/Bootup Sequence
Perform power-on self test (POST).
Load and run bootstrap code.
Find the Cisco IOS software.
Load the Cisco IOS software.
Find the configuration.
Load the configuration.
Run the configured Cisco IOS software.
Boot Sequence
ROMMonitor
RXBoot
FLASH
Configuration Register
C-File
NVRAM
Y
N
Running
Setup Mode
Checks All interfaces
RAM
0
0
0
0
0
0
0
1
0
0
1
0
ROMMonitor
RxBoot
Flash
1
1
1
1
0
1
2-15
After the Post…
After the POST, the following events occur as the router initializes:

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

Step 2
The 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 3
The operating system image is loaded.

Step 4
The 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 5
If 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.  
Loading the Cisco IOS Software
From Flash Memory
The flash memory file is decompressed into RAM.
Loading the Configuration
Load and execute the configuration from NVRAM.
If no configuration is present in NVRAM, enter setup mode.
External Components of a 2600 Router
Internal Components of a 2600 Router
Computer/Terminal Console Connection
Modem Connection to Console/Aux Port
HyperTerminal Session Properties
Establishing a
HyperTerminal 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.

Router Command Line Interface
IOS File System Overview
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.
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.
Overview of Router Modes
Router Modes
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.
Show Version Command
wg_ro_a#show version
Cisco 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 phanguye
Image text-base: 0x03050C84, data-base: 0x00001000

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

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

Configuration register is 0x2102


Viewing the Configuration
show running-config and
show startup-config Commands
wg_ro_c#show startup-config
Using 1359 out of 32762 bytes
!
version 12.0
!
-- More --
wg_ro_c#show running-config
Building configuration...

Current configuration:
!
version 12.0
!
-- More --
In NVRAM
In RAM
Displays the current and saved configuration
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
Command Abbreviation
Show Configuration – sh conf
Configure Terminal – conf t
Line auxillary – line aux
Line console – line con
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 Gates
Gates(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).
Setting
the Clock
with Help
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 command
banner motd # Welcome to Gates Training #.

Save changes by issuing the command copy run start
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
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.

Passwords
There are five passwords for Router
Privileged Mode Password – 2
Line Console Password
Auxiliary Port Password
Telnet Password
Privileged Mode Password
Gates(config)# enable password gates
Encrypted privilege mode password
Gates(config)# enable secret gates1


Line Password
Gates(config)# line console 0
Gates(config)# password cisco
Gates(config)# login





Aux Port Password
Gates(config)# line aux 0
Gates(config)# password cisco
Gates(config)# login





Connecting to Aux Port
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.

Telnet Password
Gates(config)# line vty 0 4
Gates(config)# password cisco
Gates(config)# login





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
Disable Passwords
Gates(config)# no enable password
Gates(config)# no enable secret
For the Console
Gates(config)# line con 0
Gates(config)# no password
Gates(config)# line vty 0 4
Gates(config)# no password

LAB – Interface Configuration
S0
S0
E0
10.0.0.1
10.0.0.2
30.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
A
S0
E0
40.0.0.2
40.0.0.1
B
S1
Descriptions
Setting descriptions on an interface is helpful to the administrator
Only locally significant
R1(config)#int e0
R1(config-if)#description Sales Lan
R1(config-if)#int s0
R1(config-if)#desc Wan to Mumbai
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 t
R1(config)#int e0
R1(config)#Description Connoted to Host
R1(config-if)#ip address 10.0.0.1 255.0.0.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface serial 0
R1(config-if)#ip address 20.0.0.1 255.255.255.0
R1(config-if)# bandwidth 64
R1(config-if)#clock rate 64000 (required for serial DCE only)
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#exit
R1#

On new routers, Serial 1 would be just Serial 0/1 and e0 would be f0/0.
s = serial e = Ethernet f = fast Ethernet
DCE DTE
To find out DCE or DTE
#Show controllers s 0
Viewing Configuration
To Check the status of interface
#Show IP interface brief
or
#Sh IP int brief




Saving and Erasing Configurations
To copy RAM to NVRAM
# copy run startup-config

To remove all configuration
# erase startup-config
# reload
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
Routing

The process of transferring data from one local area network to another
Layer 3 devices
Routed protocol Enables to forward packet from one router to another – Ex – IP, IPX
Routing 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

Routing
From
Raj
House #213, 4th Street
Jayanagar, Bangalore


To
Ram
House #452, 2nd Street
Dadar, Mumbai


To route, a router needs to know:
Destination addresses
Sources it can learn from
Possible routes
Best route
What is Routing?
172.16.1.0
10.120.2.0
What is Routing? (cont.)
Network
Protocol
Destination
Network
Connected
Learned

10.120.2.0
172.16.1.0

Exit Interface
E0
S0
Routed Protocol: IP

Routers must learn destinations that are not directly connected
172.16.1.0
10.120.2.0
E0
S0
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.
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
E1
10.0.0.1
10.0.0.2
A
B
20.0.0.2
20.0.0.1
LAB Configuration
S0
S0
E0
E0
10.0.0.1
10.0.0.2
30.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
A
B
LAB – Interface Configuration
S0
S0
E0
10.0.0.1
10.0.0.2
30.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
A
S0
E0
40.0.0.2
40.0.0.1
B
S1
Test The Connection
Host A can ping router R1 and R2
To enable Host A to Ping Host B we need to configure Routes
IP Routing
The different types of routing are:
Static routing
Default routing
Dynamic routing
Static Routes
Benefits
No overhead on the router CPU
No bandwidth usage between routers
Adds security

Disadvantage
Administrator must really understand the internetwork
If a network is added to the internetwork, the administrator has to add a route to it on all routers
Not feasible in large networks
R1(config)# iproute DestAddress SNM Nexthop address
R1(config)#ip route network [mask]
{address | interface}[distance] [permanent]
Static Route Configuration
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 Configuration
R1(config)#ip route 30.0.0.0 255.0.0.0 20.0.0.2
LAB – Static Route Configuration
S0
S0
E0
10.0.0.1
10.0.0.2
30.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
A
S0
E0
40.0.0.2
40.0.0.1
B
S1
R1# config t
R1(config)#ip route 30.0.0.0 255.0.0.0 20.0.0.2
R1(config)#ip route 40.0.0.0 255.0.0.0 20.0.0.2
R2# config t
R2(config)#ip route 10.0.0.0 255.0.0.0 20.0.0.1
R2(config)#ip route 40.0.0.0 255.0.0.0 30.0.0.2
R3# config t
R3(config)#ip route 10.0.0.0 255.0.0.0 30.0.0.1
R3(config)#ip route 20.0.0.0 255.0.0.0 30.0.0.1
Verifying Static
Route 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.
S0
S0
E0
10.0.0.1
10.0.0.2
30.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
A
S0
E0
40.0.0.2
40.0.0.1
B
S1
R1# config t
R1(config)#no ip route 30.0.0.0 255.0.0.0 20.0.0.2
R1(config)#no ip route 40.0.0.0 255.0.0.0 20.0.0.2
R2# config t
R2(config)#no ip route 10.0.0.0 255.0.0.0 20.0.0.1
R2(config)#no ip route 40.0.0.0 255.0.0.0 30.0.0.2
R3# config t
R3(config)#no ip route 10.0.0.0 255.0.0.0 30.0.0.1
R3(config)#no ip route 20.0.0.0 255.0.0.0 30.0.0.1
Removing IP Route
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
S0
S0
E0
E0
10.0.0.1
10.0.0.2
40.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
S0
S1
30.0.0.2
40.0.0.1
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
B
172.16.2.2
Network
A
B
This route allows the stub network to reach all known networks beyond router A.
10.0.0.0
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
S0
S0
E0
E0
10.0.0.1
10.0.0.2
40.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
S0
S1
30.0.0.2
40.0.0.1
LAB Configuration
Default Route LAB Configuration
S0
S0
E0
E0
10.0.0.1
10.0.0.2
40.0.0.2
20.0.0.1
20.0.0.2
30.0.0.1
S0
S1
30.0.0.2
40.0.0.1
R1# config t
R1(config)#ip route 0.0.0.0 0.0.0.0 20.0.0.2
R3# config t
R3(config)#ip route 0.0.0.0 0.0.0.0 30.0.0.1
R2# config t
R2(config)#ip route 10.0.0.0 255.0.0.0 20.0.0.1
R2(config)#ip route 40.0.0.0 255.0.0.0 30.0.0.2
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.
Network
Protocol
Destination
Network
Connected
RIP
IGRP

10.120.2.0
172.16.2.0
172.17.3.0
Exit Interface
E0
S0
S1
Routed Protocol: IP
Routing protocol: RIP, IGRP
172.17.3.0
172.16.1.0
10.120.2.0
E0
S0
Autonomous System
AS 2000
AS 3000
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 updates
AS 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 Categories
IGP
Interior Gateway Protocol
(IGP)
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 Categories
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
Types or Classes of Routing Protocols
Distance Vector
RIP V1
IGRP
RIP V2

Link state
OSPF

Hybrid
EIGRP
Types or Classes of Routing Protocols
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
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)
EIGRP
OSPF
IS-IS
Routers pass periodic copies of routing table to neighbor
routers and accumulate distance vectors.
Distance Vector Routing Protocols
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?
192.168.10.1
192.168.20.1
Distance Vector
There are two Distance Vector Protocol, Both uses different metric
RIP – Hops
IGRP - Composite
192.168.20.1
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

192.168.20.1
0
1
1
2
2
3
R1
Distance Vector
192.168.20.1
56 kbps
1 Mbps
1 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

R1
10
10
10
30
30
192.168.10.1
Routing Loops
A network problem in which packets continue to be routed in an endless circle
Routers discover the best path to
destinations from each neighbor.
Sources of Information and Discovering Routes
Each node maintains the distance from itself to each possible destination network.
Inconsistent Routing Entries
Slow convergence produces inconsistent routing.
Inconsistent Routing Entries (Cont.)
Router C concludes that the best path to network 10.4.0.0 is through router B.
Inconsistent Routing Entries (Cont.)
Router A updates its table to reflect the new but erroneous hop count.
Inconsistent Routing Entries (Cont.)
Hop count for network 10.4.0.0 counts to infinity.
Count to Infinity
Packets for network 10.4.0.0 bounce (loop) between routers B and C.
Routing Loops
Define a limit on the number of hops to prevent infinite loops.
Defining a Maximum
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
It is never useful to send information about a route back in the direction from which the original information came.
Split Horizon
Split Horizon
Solution to the Routing Loop problem
Split 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.
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.
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.
Triggered Updates Graphic
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
Solution: Holddown Timers
Pinhole Congestion
192.168.10.1
192.168.20.1
1Mbps
1Mbps
56kbps
56kbps
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).
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.
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 rip
Gates(config-router)#network 172.16.0.0

The network numbers are based on the network class addresses, not subnet addresses or individual host addresses.
RIP Configuration
S0
S0
E0
E0
192.168.10.1
S0
S1
R1# config t
R1(config)# )#router rip
R1(config)#network 192.168.10.0
R1(config)#network 192.168.20.0
R2# config t
R2(config)#router rip
R2(config)#network 192.168.20.0
R2(config)#network 192.168.30.0
192.168.10.2
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 t
R3(config)# )#router rip
R3(config)#network 192.168.30.0
R3(config)#network 192.168.40.0
Verifying RIP Configuration
Displaying the
IP Routing Table
debug ip rip Command
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 t
R1(config)#router rip
R1(config-router)#network 192.168.10.0
R1(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.
RIP Version 2 (RIPv2)
R1# config t
R1(config)# )#router rip
R1(config)#network 192.168.10.0
R1(config)#network 192.168.20.0
R1(config)#version 2

Exercise - RIP Version 2 Configuration
S0
S0
E0
E0
192.168.0.16/29
S0
S1
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
Exercise - RIP Version 2 Configuration
S0
S0
E0
E0
192.168.0.18
255.255.255.248
S0
S1
192.168.0.17
255.255.255.248
192.168.0.5
255.255.255.252
192.168.0.6
255.255.255.252
192.168.0.9
255.255.255.252
192.168.0.10
255.255.255.252
192.168.0.33
255.255.255.240
192.168.0.34
255.255.255.240
Exercise - RIP Version 2 Configuration
S0
S0
E0
E0
192.168.0.16/29
S0
S1
192.168.0.4/30
192.168.0.8/30
192.168.0.32/28
R2# config t
R2(config)#router rip
R2(config)#network 192.168.0.4
R2(config)#network 192.168.0.8
R2(config)#version 2
R1# config t
R1(config)# )#router rip
R1(config)#network 192.168.0.4
R1(config)#network 192.168.0.16
R1(config)#version 2

R3# config t
R3(config)# )#router rip
R3(config)#network 192.168.0.8
R3(config)#network 192.168.0.32
R3(config)#version 2

© 2002, Cisco Systems, Inc. All rights reserved.
122
Enabling IGRP
CISCO Proprietary
More scalable than RIP
Sophisticated metric
Introducing IGRP
Bandwidth
Delay
Reliability
Load
MTU
IGRP Composite Metric
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.
IGRP Vs RIP
IGRP Timers
Update timers these specify how frequently routing-update messages should be sent. The default is 90 seconds.

Invalid timers These specify how long a router should wait before declaring a route invalid if it doesn’t receive a specific update about it. The default is 3*90 = 270.

Holddown timers These specify the holddown period. The default is three times the update timer period plus 10 seconds. 280 seconds

Flush timers These indicate how much time should pass before a route should be flushed from the routing table. The default is seven times the routing update period. If the update timer is 90 seconds by default, then 7 × 90 = 630 seconds elapse before a route will be flushed from the route table.
Configuring IGRP
IGRP Configuration
S0
S0
E0
E0
192.168.10.1
S0
S1
R1# config t
R1(config)# )#router igrp 10
R1(config)#network 192.168.10.0
R1(config)#network 192.168.20.0
R2# config t
R2(config)#router igrp 10
R2(config)#network 192.168.20.0
R2(config)#network 192.168.30.0
192.168.10.2
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 t
R3(config)# )#router igrp 10
R3(config)#network 192.168.30.0
R3(config)#network 192.168.40.0
Verifying the IGRP Routing Tables
LabA#sh ip route
[output cut]
I 192.168.50.0 [100/170420] via 192.168.20.2, Serial0/0
I 192.168.40.0 [100/160260] via 192.168.20.2, Serial0/0
I 192.168.30.0 [100/158360] via 192.168.20.2, Serial0/0
C 192.168.20.0 is directly connected Serial0/0
C 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 routes
clear ip route
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