Performance and Fault Management

Setting Up a Loopback Interface

One of the best-kept secrets at Cisco is the use of the Loopback0 interface on a router. The Loopback interface does not apply to Cisco Catalyst switches. The sc0 port on the Catalyst switch acts like a Loopback interface because it is the only IP address assigned to the whole switch. The configuring of the Loopback interface on a router is the recommended use in many IOS features, such as RSRB, DLSW, logging, NTP, and SNMP.

The Loopback interface is a virtual interface on the router that acts as a logical system interface that is, in essence, assigned to the router as one node instead of a multiple interface router. It stays up as long as the router is operational. It has no relationship to any physical interfaces ...