18Configuring a null interfaceA null interface is a virtual interface and is always up, but you can neither use it to forward data packetsnor can you configure it with an IP address or link layer protocol. The null interface provides a simplerway to filter packets than ACL. You can filter undesired traffic by transmitting it to a null interface insteadof applying an ACL. For example, if you specify a null interface as the next hop of a static route to aspecific network segment, any packets routed to the network segment are dropped.To configure a null interface:Step Command Remarks1. Enter system view. system-view N/A2. Enter null interface view. interface null 0Interface Null 0 is the default nullinterface on the device and cannotbe manually created or removed.Only one null interface, Null 0, issupported on the device. The nullinterface number is always 0.3. Set the interface description. description text The default setting is NULL0 Interface.4. Restore the default settings forthe null interface. default N/AConfiguring an inloopback interfaceAn inloopback interface is a virtual interface created by the system, which cannot be configured ordeleted. The physical layer and link layer protocol states of an inloopback interface are always up. AllIP packets sent to an inloopback interface are considered packets sent to the device itself and are notfurther forwarded.Displaying and maintaining loopback, null, andinloopback interfacesExecute display commands in any view and reset commands in user view.Task CommandDisplay information about the specified or allloopback interfaces.display interface [ loopback [ interface-number ] ] [ brief[ description ] ]display interface [ loopback ] [ brief [ down ] ]Display information about the null interface. display interface [ null [ 0 ] ] [ brief [ description ] ]Display information about the inloopbackinterface. display interface [ inloopback [ 0 ] ] [ brief [ description ] ]Clear the statistics on the specified or all loopbackinterfaces. reset counters interface loopback [ interface-number ]
