H3C Technologies H3C WX5500E Series Access Controllers - Manual (Page 28)

17
Configuring the null interface
A null interface is a completely software-based logical interface, and is always up. However, you cannot
use it to forward data packets or configure an IP address or link layer protocol on it. With a null interface
specified as the next hop of a static route to a specific network segment, any packets routed to the
network segment are dropped. The null interface provides a simpler way to filter packets than ACL. You
can filter uninteresting traffic by transmitting it to a null interface instead of applying an ACL.
For example, by executing the ip route-static 92.101.0.0 255.255.0.0 null 0 command (which configures
a static route leading to null interface 0), you can have all packets destined to the network segment
92.101.0.0/16 discarded.
Only one null interface, Null 0, is supported on your device. You cannot remove or create a null
interface.
To enter null interface view:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter null interface
view.
interface null 0
The Null 0 interface is the default null interface
on your device. It cannot be manually created
or removed.
3. Set the interface
description.
description text
Optional.
By default, the description of a null interface is
interface name Interface.
4. Restore the default
settings for the null
interface.
default Optional.
Displaying and maintaining loopback and null
interfaces
Task Command Remarks
Display information about loopback
interfaces.
display interface [ loopback ] [ brief
[ down ] ] [ | { begin | exclude |
include } regular-expression ]
display interface loopback
interface-number [ brief ] [ | { begin |
exclude | include } regular-expression ]
Available in any view.
Display information about the null
interface.
display interface [ null ] [ brief [ down ] ]
[ | { begin | exclude | include }
regular-expression ]
display interface null 0 [ brief ] [ |
{ begin | exclude | include }
regular-expression ]
Available in any view.
Clear the statistics on a loopback
interface. reset counters interface [ loopback
[ interface-number ] ]
Available in user view.