Loopback InterfacesA Loopback interface is a virtual interface in which the software emulates an interface. Packets routed toit are processed locally.Because this interface is not a physical interface, you can configure routing protocols on this interface toprovide protocol stability. You can place Loopback interfaces in default Layer 3 mode.To configure, view, or delete a Loopback interface, use the following commands.• Enter a number as the Loopback interface.CONFIGURATION modeinterface loopback numberThe range is from 0 to 16383.• View Loopback interface configurations.EXEC modeshow interface loopback number• Delete a Loopback interface.CONFIGURATION modeno interface loopback numberMany of the same commands found in the physical interface are also found in the Loopback interfaces.Null InterfacesThe Null interface is another virtual interface. There is only one Null interface. It is always up, but notraffic is transmitted through this interface.To enter INTERFACE mode of the Null interface, use the following command.• Enter INTERFACE mode of the Null interface.CONFIGURATION modeinterface null 0The only configurable command in INTERFACE mode of the Null interface is the ip unreachablecommand.Port Channel InterfacesPort channel interfaces support link aggregation, as described in IEEE Standard 802.3ad.This section covers the following topics:• Port Channel Definition and Standards• Port Channel Benefits• Port Channel Implementation• Configuration Tasks for Port Channel InterfacesInterfaces 331
