What is IGRP and how to Configure IGRP

What is IGRP

IGRP (Interior Gateway Routing Protocol) is a Cisco-proprietary distance-vector routing protocol that means all the routers must be Cisco routers to use IGRP in your network. The main purpose of creating this protocol is to overcome the problems associated with RIP. The maximum hope count of IGRP is 255 with the default being 100 same as EIGRP. In large networks, this is helpful to solve the problem of 15 hops being the maximum possible in a RIP network.

By default, the delay of line and bandwidth is the metric of IGRP for determining the best route to the internetwork which means it is known as a composite metric. MTU (Maximum Transmission Unit), load, and reliability can also be used but not as a default.

Note: In GNS3 or Packet Tracer you won’t find the IGRP because the Cisco no longer supports the IGRP.

How to Configure IGRP

How to Configure IGRP

The main configuration difference between IGRP and RIP is that you supply the AS (Autonomous System) number when you configure IGRP. All the routers use the same IGRP number to share the information of the routing table with all connected neighbors.

RIP vs IGRP Comparison

Configuring the Router R1 Interfaces

Router> enable

Router# configure terminal

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

Router (config) # hostname R1

R1 (config) # interface serial 0/1/0

OR

R1 (config) # int s 0/1/0

R1 (config-if) # ip address 192.168.2.1 255.255.255.0

R1 (config-if) #encapsulation hdlc

R1 (config-if) #clock rate 64000

R1 (config-if) #keepalive 12

R1 (config-if) #no shutdown

R1 (config-if) #

OR

R1 (config-if) #no shut

%LINK-5-CHANGED: Interface Serial0/1/0, changed state to down

R1 (config-if) #exit

R1 (config) # interface fastethernet0/0

OR

R1 (config) # int fa0/0

R1 (config-if) # ip address 192.168.1.10 255.255.255.0

R1 (config-if) #no shutdown

Interface Status up

R1 (config-if) #end

R1#

Configuring the Router R2 Interfaces

Router> enable

Router# configure terminal

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

Router (config) # hostname R2

R2 (config) # interface serial 0/1/0

OR

R2 (config) # int s 0/1/0

R2 (config-if) # ip address 192.168.2.2 255.255.255.0

R2 (config-if) #encapsulation hdlc

R2 (config-if) #keepalive 12

R2 (config-if) #no shutdown   

OR

R2 (config-if) #no shut

Interface Status up

R2 (config-if) #exit

R2 (config) # interface fastethernet0/0

OR

R2 (config) # int fa0/0

R2 (config-if) # ip address 192.168.4.10 255.255.255.0

R2 (config-if) #no shutdown

Interface Status up

R2 (config-if) #end

R2#

Router R1 and R2 Routing Table

Router R1

R1# show ip route

IP Route Status

Note: By default, in the router R1 routing table the two associated interfaces and directly connected networks are listed.

Router R2

R2# show ip route

IP Route Status

Note: By default, in the router R2 routing table the two associated interfaces and directly connected networks are listed.

Ping Verification on Router R1 and R2

Router R1

R1#ping 192.168.2.2

Successful Ping Verification

R1#ping 192.168.4.10

Unsuccessful Ping Verification

Note: The ping was not successful because the network 192.168.4.0 is not listed in the router R1 routing table. Using the IGRP (Interior Gateway Routing Protocol) the network 192.168.4.0 needs to be put in the R1 routing table.

Router R2

R2#ping 192.168.2.1

Successful Ping Verification

R2#ping 192.168.1.10

Unsuccessful Ping Verification

Note: The ping was not successful because the network 192.168.1.0 is not listed in the router R2 routing table. Using the IGRP (Interior Gateway Routing Protocol) the network 192.168.1.0 needs to be put in the R2 routing table.

                                   Configuring IGRP on Router R1 and R2

Router R1

R1#configure terminal

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

R1 (config) #router igrp?

<1-65535> Autonomous system number

R1 (config) #router igrp 5

R1 (config-router) #network 192.168.2.0

R1 (config-router) #network 192.168.1.0

R1 (config-router) #end

R1#

Note: The autonomous number on IGRP running routers must be the same so that they can share routing information.

Router R2

R2#configure terminal

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

R2 (config) #router igrp 5

R2 (config-router) #network 192.168.2.0

R2 (config-router) #network 192.168.4.0

R2 (config-router) #end

R2#

Router R1 and R2 Routing Table

Router R1

R1#show ip route

IP Route Status

R1#

Router R2

R2#show ip route

IP Route Status

R2#

Note: Metric value is 8486. Administrative distance is 100 and the word “I” represents the IGRP.

Ping Verification on Router R1 and R2

Router R1

R1#ping 192.168.4.10

Successful Ping Verification

R1#

Router R2

R2#ping 192.168.1.10

Successful Ping Verification

R2#

IP Protocol Verification on Router R1

R1#show ip protocols

IP Protocol Status

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If you want to configure EIGRP then Visit: 👇

How to Configure EIGRP

If you want to configure and Practical Lab of Static and Dynamic Routing then visit below link: 👇

How to Configure Static Routing

Dynamic Routing

Redistribution of Routes in Dynamic Routing

How to Configure OSPF Multi-area

How to Configure OSPF Single-area

How to Configure EIGRP

How to Configure RIPv2

How to Configure RIPv1