IGRP Interior Gateway Routing Protocol

IGRP is an advanced distance vector protocol developed by Cisco.

Characteristic of IGRP ( Interior Gateway Routing Protocol )

Increase scalability is improved for Routing in large size network compared to network that use in RIP.
Hops count IGRP has a default maximum hops count of 100, hops configure to the maximum of 255 hops.
Multiple path IGRP can maintain up to 6 equal part between network source and destination.

Here as number is autonomous number system it can be between 12655 3584 router needed in the share routing information this should belong to the same as IP Network in tonight’s class network number.
Unique number identifying the routing domain of the router range from
A autonomous system number is a collection of network and the second administrative domain

Two main purposes of IGRP are:

1) Its Communicate routing information to all connected routers within its boundary or autonomous system.
2) It will update if ever topology of network changed.

In every 90 seconds it send notification of new changes to its neighbors.

Interior Gateway Routing Protocol (IGRP)

considering we have configure Hostname and IP address in Router01,Router03,Router03
Please refer how to configure Hostname and IP address in Router01,Router03,Router03 by clicking here.

Interior Gateway Routing Protocol (IGRP) configuration in Router01

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)# router igrp 1
Router01(config-router)# network 172.16.0.0
Router01(config-router)# network 172.17.0.0
Router01(config-router)#exit
Router01(config)#exit
Router01#

Interior Gateway Routing Protocol (IGRP) configuration in Router02

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router02(config)# router igrp 1
Router02(config-router)# network 172.17.0.0
Router02(config-router)# network 172.18.0.0
Router02(config-router)# network 172.19.0.0
Router02(config-router)#exit
Router02(config)#exit
Router02#

Interior Gateway Routing Protocol (IGRP) configuration in Router03

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Router03(config)# router igrp 1
Router03(config-router)# network 172.19.0.0
Router03(config-router)# network 172.20.0.0
Router03(config-router)#exit
Router03(config)#exit
Router03#

How to view the routing table in Router01

Router01>enable
Router01#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
C 172.16.0.0/16 is directly connected, FastEthernet0/0
C 172.17.0.0/16 is directly connected, Serial0/0
I 172.18.0.0/16 [120/1] via 172.17.0.2, 00:00:22, Serial0/0
I 172.19.0.0/16 [120/1] via 172.17.0.2, 00:00:22, Serial0/0
I 172.20.0.0/16 [120/2] via 172.17.0.2, 00:00:22, Serial0/0

How to view the routing table in Router02

Router02>enable
Router02#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
72.16.0.0/16 [120/1] via 172.17.0.1, 00:00:07, Serial0/0
C 172.17.0.0/16 is directly connected, Serial0/0
C 172.18.0.0/16 is directly connected, FastEthernet0/0
C 172.19.0.0/16 is directly connected, Serial0/1
I 172.20.0.0/16 [120/1] via 172.19.0.2, 00:00:20, Serial0/1
I 172.16.0.0/16 [120/1] via 172.17.0.1, 00:00:20, Serial0/0

How to view the routing table in Router03

Router03>enable
Router03#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
I 172.16.0.0/16 [120/2] via 172.19.0.1, 00:00:02, Serial0/1
I 172.17.0.0/16 [120/1] via 172.19.0.1, 00:00:02, Serial0/1
I 172.18.0.0/16 [120/1] via 172.19.0.1, 00:00:02, Serial0/1
C 172.19.0.0/16 is directly connected, Serial0/1
C 172.20.0.0/16 is directly connected, FastEthernet0/0

Verify the connectivity between networks using the ping command

To verify the Interior Gateway Routing Protocol (IGRP) routes and the connectivity between networks, run the ping command from Host01 (IP address: 172.16.0.10/16) to Host03 (IP address: 172.20.0.10/16).

C:\>ping 172.20.0.10

Pinging 172.20.0.10 with 32 bytes of data:

Reply from 172.20.0.10: bytes=32 time=172ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125
Reply from 172.20.0.10: bytes=32 time=157ms TTL=125
Reply from 172.20.0.10: bytes=32 time=188ms TTL=125

The ping reply from Host03 (IP address: 172.20.0.10/16) shows that the Interior Gateway Routing Protocol (IGRP) is configured well in three routers and there is network connectivity between different networks.