18
NOTE:
You can configure settings such as IP addresses and IP routes on loopback interfaces. For more
information, see the
Layer 3—IP Services Configuration Guide
and
Layer 3—IP Routing Configuration
Guide
.
Null interface
Introduction to 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 that leads to null interface 0), you can have all the packets destined to the network segment
92.101.0.0/16 discarded.
Only one null interface, Null 0, is supported on your switch. You cannot remove or create a null interface.
Configuring null 0 interface
Follow these steps to enter null interface view:
Enter null interface view
Required
The Null 0 interface is the default null interface
on your switch. It cannot be manually created
or removed.
Set a description for the
null interface
Optional
By default, the description of an interface is
the interface name followed by the ―Interface‖
string.
Displaying and maintaining loopback and null
interfaces
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 ]
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