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JunosE 11.3.x IP Services Configuration Guide
Using the Null Interface
interface null
ip route
Prefix Lists
32
You can use access control lists to filter undesired traffic. Another way to handle undesired
traffic is to send it to the null interface. The router automatically creates the null interface,
which is always up, cannot be deleted, and acts as a data sink. In other words, the null
interface cannot forward or receive traffic. However, the CLI does allow you to access
the null interface.
The E Series router creates the null interface by default; you do not have to manually
create it. You can direct traffic to the null interface by specifying the null 0 keywords
instead of a next-hop or destination address when you configure routes.
Use to access the null interface.
The null interface is a data sink; it does not accept or forward traffic.
Although you can access the null interface, you cannot configure any values for it or
delete it.
Example
host1(config)#interface null 0
host1(config-if)#
There is no no version.
See interface null.
Use to configure a static route and redirect traffic from it to the null interface.
Example
host1(config-if)#ip route 10.10.20.5 null 0
Use the no version to remove the static route.
See ip route.
A prefix list is a sequential collection of permit and deny conditions that apply to IP or
IPv6 addresses. Like an access list, the router tests addresses one by one against the
conditions in a prefix list. The first match determines whether the router accepts or rejects
the address. Because the router stops testing conditions after the first match, the order
of the conditions is critical. If no conditions match, the router rejects the address. An
empty prefix list results in an automatic permit of the tested address.
Unlike access lists, the prefix list specifies a base IP or IPv6 address and a length (the
number of bits applied to the base to determine the network prefix). The tested address
is matched against the prefix.
Copyright © 2010, Juniper Networks, Inc.
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