Description: The purpose of this Lab is to configure a loop back interface and test it for connectivity.
The loopback interface is a logical interface internal to a router. It is not connected to any other device. A loopback interface is UP as long as the router is up and running. It is useful in managing a router as there will always be at least one interface available on the router, irrespective other physical interfaces.
The command used for assigning loopback interface is
Router(config)#interface loopback <number>
The number can be between 0 and 2147483647
A loopback interface is automatically put in "no shutdown" state when created. However, you need to assign an ip address to use a loopback interface.
1. Configure s0 on R1 with ip address and subnet mask as shown in the diagram.
2. Configure s0 and loopback 1 on router R2 as shown in the diagram.
3. Ping loopback 1 and verify connectivity.
(config)# int ser 0
(config-in)#ip address 192.168.1.1 255.255.255.0
(config)#int ser 0
(config-if)#ip address 220.127.116.11 255.255.255.0
(config)#interface loopback 1
(config-if)#ip address 192.168.1.10 255.255.255.0
<you should get successful ping response>