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How to configure Interior Gateway Routing Protocol (IGRP)

If you are not familiar with Interior Gateway Routing Protocol (IGRP), click the following link to view an introduction to Interior Gateway Routing Protocol (IGRP).

 

Interior Gateway Routing Protocol (IGRP) Configuration

Interior Gateway Routing Protocol (IGRP) can be configured in a router using the following IOS commands. If you have a new router with a latest IOS release, you may not find Interior Gateway Routing Protocol (IGRP) configuration commands because Interior Gateway Routing Protocol (IGRP) is removed from new IOS releases.

Router(config)# router igrp ASN
Router(config-router)# network Network_ID

ASN in the above IOS command stands for Autonomous System Number.

Interior Gateway Routing Protocol (IGRP) - Lab Practice

The following diagram shows our lab setup. We have three routers, three switches and three hosts connected as below. The host names, IP addresses and the interfaces of the routers are shown in diagram. The IP addresses of the hosts are also shown in the diagram.

CCNA Routing lab setup

If you are not familiar with a router console connection, click the following link to learn how to connect the serial port of your computer to router console port.

Click the following link to learn how to connect to the console port of the router if there is no serial port in your computer.

Click the following links to learn how to use HyperTerminal terminal emulator and PuTTY terminal emulator to configure router.

Hostname and IP address configuration in Router01

Connect to Router01 console and use the following IOS commands to configure host name as Router01.

Router>enable
Router#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname Router01
Router01(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router01 and configure IP address as 172.16.0.1/16.

Router01>enable Router01#configure terminal Enter configuration commands, one per line. End with CNTL/Z.
Router01(config)#interface fa0/0
Router01(config-if)#ip address 172.16.0.1 255.255.0.0
Router01(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router01 and configure IP address as 172.17.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/0 interface, since this is the DCE side.

Router01>enable
Router01#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router01(config)#interface s0/0
Router01(config-if)#clock rate 64000
Router01(config-if)#ip address 172.17.0.1 255.255.0.0
Router01(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router02

Connect to Router02 console and use the following IOS commands to configure host name as Router02.

Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname Router02
Router02(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router02 and configure IP address as 172.18.0.1/16.

Router02>enable 
Router02#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router02(config)#interface fa0/0
Router02(config-if)#ip address 172.18.0.1 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/0 configuration mode on Router02 and configure IP address as 172.17.0.2/16.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router02(config)#interface s0/0
Router02(config-if)#ip address 172.17.0.2 255.255.0.0
Router02(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router02 and configure IP address as 172.19.0.1/16. You have to set a clock rate also using the "clock rate" command on S0/1 interface, since this is the DCE side.

Router02>enable
Router02#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router02(config)#interface s0/1
Router02(config-if)#clock rate 64000
Router02(config-if)#ip address 172.19.0.1 255.255.0.0
Router02(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Hostname and IP address configuration in Router03

Connect to Router03 console and use the following IOS commands to configure host name as Router03.

Router>enable
Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#hostname Router03
Router03(config)#

Use the following IOS commands to open the fast ethernet interface Fa0/0 configuration mode on Router03 and configure IP address as 172.20.0.1/16.


Router03>enable
Router03#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router03(config)#interface fa0/0
Router03(config-if)#ip address 172.20.0.1 255.255.0.0
Router03(config-if)#no shutdown

Use the following IOS commands to open the serial interface S0/1 configuration mode on Router03 and configure IP address as 172.19.0.2/16.

Router03>enable
Router03#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router03(config)#interface s0/1
Router03(config-if)#ip address 172.19.0.2 255.255.0.0
Router03(config-if)#no shutdown

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Interior Gateway Routing Protocol (IGRP) configuration in Router01

Connect to Router01 console and use the following IOS commands to configure Interior Gateway Routing Protocol (IGRP) in Router01. Please refer the beginning of this lesson to view the Interior Gateway Routing Protocol (IGRP) configuration IOS command.

In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

                    
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#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Interior Gateway Routing Protocol (IGRP) configuration in Router02

Connect to Router02 console and use the following IOS commands to configure Interior Gateway Routing Protocol (IGRP) in Router02. Please refer the beginning of this lesson to view the Interior Gateway Routing Protocol (IGRP) configuration IOS command.

In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

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#

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

Interior Gateway Routing Protocol (IGRP) configuration in Router03

Connect to Router03 console and use the following IOS commands to configure Interior Gateway Routing Protocol (IGRP) in Router03. Please refer the beginning of this lesson to view the Interior Gateway Routing Protocol (IGRP) configuration IOS command.

In the IOS "network" command, shown below, we specify only the directly connected networks of this router.

                    
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#         

Do remember to run the "copy running-config startup-config" command from enable mode, if you want to save the changes you have made in the router.

How to view the routing table in Router01

After the network is converged after the initial configuration and Interior Gateway Routing Protocol (IGRP) configuration, we can use the "show ip route" to view the routing table in Router01, as shown below.

                    
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

The "I" character at the beginning of a line in routing table shows that it is a route discovered byInterior Gateway Routing Protocol (IGRP) and "C" character shows that it is a directly connected network.

How to view the routing table in Router02

When the network is converged after the initial configuration and Interior Gateway Routing Protocol (IGRP) configuration, we can use the "show ip route" to view the routing table in Router02, as shown below.

                    
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
172.16.0.0/16 [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

The "I" character at the beginning of a line in routing table shows that it is a route discovered by Interior Gateway Routing Protocol (IGRP) and "C" character shows that it is a directly connected network.

How to view the routing table in Router03

When the network is converged after the initial configuration and Interior Gateway Routing Protocol (IGRP) configuration, we can use the "show ip route" to view the routing table in Router03, as shown below.

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

The "I" character at the beginning of a line in routing table shows that it is a route discovered by Interior Gateway Routing Protocol (IGRP) and "C" character shows that it is a directly connected network.

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

Ping statistics for 172.20.0.10:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 157ms, Maximum = 188ms, Average = 176ms

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.

Related Tutorials
• Introduction to Static Routes and Default Routes
• How to configure Static Routes and Default Routes
• What is Dynamic Routing and different types of Dynamic Routing
• Introduction to Distance Vector Routing Protocols
• How to configure Routing Information Protocol (RIP)
• Introduction to Interior Gateway Routing Protocol (IGRP)
• Introduction to Link State Routing Protocols
• Introduction to Open Shortest Path First (OSPF) Protocol
• How to configure Open Shortest Path First (OSPF)
• Introduction to Hybrid Routing Protocols
• Introduction to Enhanced Interior Gateway Routing Protocol (EIGRP)
• How to configure Enhanced Interior Gateway Routing Protocol (EIGRP)