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Using a Loopback Interface

The loopback interface provides a stable address for protocols (for example, BGP, Telnet, or LDP) to use so that they can avoid any impact if a physical interface goes down.

The loopback interface sends packets back to the router or access server for local processing. Any packets routed from the loopback interface, but not destined to the loopback interface, are dropped.



Note: Do not confuse loopback with the null 0 interface. Traffic routed to null 0 is discarded on the line card.

The no version deletes the loopback interface.

    interface loopback

host1(config)#interface loopback 20
host1(config-if)#ip address 10.10.20.5 255.255.255.254

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