23
Configuring a null interface
A null interface is a virtual interface and is always up, but you cannot use it to forward data packets or
configure it with an IP address or link layer protocol. The null interface provides a simpler way to filter
packets than ACL. You can filter undesired traffic by transmitting it to a null interface instead of applying
an ACL. For example, if you specify a null interface as the next hop of a static route to a network segment,
any packets routed to the network segment are dropped.
To configure a null interface:
Step Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enter null interface view.
interface null 0
Interface Null 0 is the default null interface on the
device and cannot be manually created or
removed.
Only one null interface, Null 0, is supported on the
device. The null interface number is always 0.
3.
Set the interface description.
description
text
The default setting is NULL0 Interface.
4.
Restore the default settings for
the null interface.
default
N/A
Configuring an inloopback interface
An inloopback interface is a virtual interface created by the system, which cannot be configured or
deleted. The physical layer and link layer protocol states of an inloopback interface are always up. All
IP packets sent to an inloopback interface are considered packets sent to the device itself and are not
forwarded.
Displaying and maintaining loopback, null, and
inloopback interfaces
Execute
display
commands in any view and
reset
commands in user view.
Task Command
Display information about the specified or all
loopback interfaces.
display interface
[
loopback
[
interface-number
] ] [
brief
[
description
|
down
] ]
Display information about the null interface.
display interface
[
null
[
0
] ] [
brief
[
description
] ]
Display information about the inloopback
interface.
display interface
[
inloopback
[
0
] ] [
brief
[
description
] ]
Clear the statistics on the specified or all loopback
interfaces.
reset counters interface
loopback
[
interface-number
]
Clear the statistics on the null interface.
reset counters interface
[
null
[
0
] ]
