3Com S7902E, Configuration Manual

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To do… Use the command… Remarks
Create a Loopback interface
and enter Loopback interface
view
interface loopback
interface-number
—
Set a description for the
loopback interface
description text
Optional
By default, the description of an
interface is the interface name
followed by the “Interface”
string.
Shut down the loopback
interface
shutdown
Optional
A loopback interface is up on
being created.
z
The subnet mask of the IP address assigned to a Loopback interface can only be 32 bits in
length.
z
Parameters such as IP addresses and IP routes can be configured on Loopback interfaces. Refer
to the IP Services Volume for detailed configurations.
Null Interface
Introduction to Null Interface
A null interface is a completely software-based logical interface. A null interface is always up. However,
you can neither use it to forward data packets nor 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 you a simpler way to
filter packets than ACL. That is, 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 the packets destined to the
network segment 92.101.0.0/16 discarded.
Currently, only one null interface, that is, Null 0 is supported on your device. You can neither remove
this null interface nor create a new one.
Configuring Null 0 Interface
Follow these steps to enter null interface view:
To do… Use the command… Remarks
Enter system view system-view —