Reference Guide

• After a route matches a filter, the filter’s action is applied. No additional filters are applied to the route.
Implementation Information
In Dell Networking OS, prefix lists are used in processing routes for routing protocols (for example, router
information protocol [RIP], open shortest path first [OSPF], and border gateway protocol [BGP]).
NOTE: It is important to know which protocol your system supports prior to implementing prefix-
lists.
Configuration Task List for Prefix Lists
To configure a prefix list, use commands in PREFIX LIST, ROUTER RIP, ROUTER OSPF, and ROUTER BGP
modes.
Create the prefix list in PREFIX LIST mode and assign that list to commands in ROUTER RIP, ROUTER
OSPF and ROUTER BGP modes.
The following list includes the configuration tasks for prefix lists, as described in the following sections.
• Configuring a prefix list
• Use a prefix list for route redistribution
For a complete listing of all commands related to prefix lists, refer to the Dell Networking OS Command
Line Interface Reference Guide.
Creating a Prefix List
To create a prefix list, use the following commands.
1. Create a prefix list and assign it a unique name.
You are in PREFIX LIST mode.
CONFIGURATION mode
ip prefix-list prefix-name
2. Create a prefix list with a sequence number and a deny or permit action.
CONFIG-NPREFIXL mode
seq sequence-number {deny | permit} ip-prefix [ge min-prefix-length] [le
max-prefix-length]
The optional parameters are:
• ge min-prefix-length: the minimum prefix length to match (from 0 to 32).
• le max-prefix-length: the maximum prefix length to match (from 0 to 32).
Example of Assigning Sequence Numbers to Filters
If you want to forward all routes that do not match the prefix list criteria, configure a prefix list filter to
permit all routes (permit 0.0.0.0/0 le 32). The “permit all” filter must be the last filter in your prefix
list. To permit the default route only, enter
permit 0.0.0.0/0.
The following example shows how the seq command orders the filters according to the sequence
number assigned. In the example, filter 20 was configured before filter 15 and 12, but the
show config
command displays the filters in the correct order.
Access Control Lists (ACLs)
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