Create,
Configure, and Test a Loopback Interface.
Lab
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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>