Description: The purpose of this exercise 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 of 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.
Network Diagram :
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
R1(config)# interface serial 0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R2(config)#interface serial 0
R2(config-if)#ip address 192.168.1.2 255.255.255.0
R2(config)#interface loopback 1
R2(config-if)#ip address 192.168.1.10 255.255.255.0
Type escape sequence to abort. Sending 5,100-byte ICMP Echos to 192.168.1.10 , Timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 6/6/6 ms