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 module.

The no version deletes the loopback interface.

interface loopback

• Use to access and configure the loopback interface.
• Provides a stable address to minimize impact of a physical interface going down.
• Example

  host1(config)#interface loopback 20

  host1(config-if)#ip address 10.10.20.5 255.255.255.254

• Use the no version to delete the loopback interface.
• See interface loopback.

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