IGRP (Interior Gateway Routing Protocol)

ABOUT IGRP PROTOCOL

IGRP stands for Interior Gateway Routing Protocol. It is also a distance vector routing protocol that uses bandwidth, delay, load, and reliability as it's matrix to calculate the best path for sending data. By default, IGRP composite matrix is delay (a sum of segments delay) and bandwidth (bandwidth of lowest segment). Maximum hop count limit is 255 (default is 100). Autonomous system (AS) number for IGRP is 100. IGRP uses IP protocol number 9 for communication and it supports only classful IP addresses.

POINTS TO BE REMEMBER

Full form: Interior Gateway Routing Protocol (IGRP)

Nature: Distance vector

Matrix: Composite (bandwidth, delay, load, and reliability) default is bandwidth and delay
Hop count limit: maximum 255 hops but default is 100 hops
AS Number: 100
Protocol Number: 9

STEPS FOR ROUTING

For Router-1

Router1(config)# router igrp
Router1(config-router)# network 10.0.0.0                              (connected network)
Router1(config-router)# network 40.0.0.0                              (connected network)
Router1(config-router)# end
Router1# write


For Router-2

Router2(config)# router igrp
Router2(config-router)# network 40.0.0.0                              (connected network)
Router2(config-router)# network 50.0.0.0                              (connected network)
Router2(config-router)# network 20.0.0.0                              (connected network)
Router2(config-router)# end
Router2# write


For Router-3


Router3(config)# router igrp
Router3(config-router)# network 50.0.0.0                              (connected network)
Router3(config-router)# network 30.0.0.0                              (connected network)
Router3(config-router)# end
Router3# write

To show routing table

Router# show ip route

To show IGRP protocol

Router# show ip protocol

RIP vs IGRP

1. RIP uses only hop count matrix to calculate the best path while IGRP uses bandwidth, delay, load, and reliability as it's matrix (default bandwidth and delay)

2. Maximum hop count limit of RIP is 15 and for IGRP is 255 (default is 100)

3. AS number of RIP is 120 and for IGRP is 100

IGRP TIMERS

1. Route Update Timer (90 seconds)

2. Route Invalid Timer (270 seconds)

3. Hold Down Timer (280 seconds)

4. Flush Timer (630 seconds)