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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 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.

Commands:

R1:
>enable
#conf term
(config)# int ser 0
(config-in)#ip address 192.168.1.1 255.255.255.0
(config-in)#no shutdown
(Config-in)#end
#

R2:
>enable
(config)#int ser 0
(config-if)#ip address 192.158.1.2 255.255.255.0
(config-if)#no shutdown
(config-if)#exit
(config)#interface loopback 1
(config-if)#ip address 192.168.1.10 255.255.255.0
(config-if)#end
#

R1:
>enable
#ping 192.168.1.10
<you should get successful ping response>

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