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Create, Configure, and Test a Loopback Interface

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.

Network Diagram:

Instructions:

1. Configure s0/0 on R1 with ip address and subnet mask as shown in the diagram

2. Configure s0/0 and loopback 1 on router R2 as shown in the diagram

3. Ping loopback 1 and verify connectivity

R1>enable
R1#conf term
R1(config)# int serial 0/0
R1(config-if)#ip address 192.168.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(Config-if)#end
R1#

R2>enable
R2#conf term
R2(config)#int serial 0/0
R2(config-if)#ip address 192.168.1.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface loopback 1
R2(config-if)#ip address 192.168.1.10 255.255.255.0
R2(config-if)#end
R2#

R1>enable
R1#ping 192.168.1.10

<you should get successful ping response>


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