Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Configure null interfaces

Updated: September 8, 2026

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This topic describes how to configure a basic null interface on the Cisco 8000 Series Router by entering global configuration mode, entering the Null 0 interface configuration mode, saving the configuration, and verifying the interface.

Configure a basic null interface to serve as an always-up sink that discards undesired traffic without the overhead of an access list.

Procedure

  1. Enter global configuration mode using the configure command.

    Example:

    Router# configure

  2. Enter the Null 0 interface configuration mode.

    Example:

    Router(config)# interface null 0

  3. Save the configuration changes using the end command.

    Example:

    Router(config-null0)# end

  4. Verify the configuration of the null interface.

    Example:

    
Router# show interfaces Null 0

Null0 is up, line protocol is up
 Hardware is Null interface
 Internet address is Unknown
 MTU 1500 bytes, BW Unknown
   reliability 0/255, txload Unknown, rxload Unknown
 Encapsulation Null, loopback not set
 Last clearing of "show interface" counters never
 5 minute input rate 0 bits/sec, 0 packets/sec
 5 minute output rate 0 bits/sec, 0 packets/sec
   0 packets input, 0 bytes, 0 total input drops
   0 drops for unrecognized upper-level protocol
   Received 0 broadcast packets, 0 multicast packets
   0 packets output, 0 bytes, 0 total output drops
   Output 0 broadcast packets, 0 multicast packets