Prefix Trees; Using A Prefix Tree - Juniper JUNOSE 11.2.X IP SERVICES Configuration Manual

Prefix Trees

Using a Prefix Tree

clear ip prefix-tree
Copyright © 2010, Juniper Networks, Inc.
Use to match any routes that have a next-hop router address passed by the specified
access list or prefix list.
Example
host1(config-route-map)#match ipv6 next-hop prefix-list next1
Use the no version to delete all next-hop match clauses from a route map unless you
specify an access list or prefix list, in which case the router removes only the list match
from the route map.
See match ipv6 next-hop.
A prefix tree is a nonsequential collection of permit and deny conditions that apply to IP
addresses. Like a prefix list, the prefix tree specifies a base IP 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. The prefix tree also enables route summarization.
However, the prefix tree does not match addresses one by one in sequence against the
listed conditions. The router performs a binary search against the tree structure of the
entries. If the tested address is less than a particular entry, it branches one way to another
test pair; if it is greater than the entry, it branches the other way to another mutually
exclusive test pair. The router stops testing conditions when it finds the best match. If
no conditions match, the router rejects the address. An empty prefix tree results in an
automatic permit of the tested address.
The prefix tree provides a faster search method and matches the test address more
closely than either the access list or the prefix list.
Use the ip prefix-tree command to define an IP prefix tree. Use the prefix-tree keyword
with the match ip address or match ip next-hop commands to add a clause to a route
map. Use the match-set summary prefix-tree command to specify the prefix tree that
summarizes routes for a particular route map.
The following example creates a prefix tree that permits routes with a prefix length of
24 or larger in the 10.10.2.0/24 network:
host1(config)#ip prefix-tree xyz permit 10.10.2.0/24
Use to clear all hit counts in the prefix trees or the specified entry from the specified
prefix tree. (The router increments the hit count by 1 each time an entry matches.)
Example
host1#clear ip prefix-tree xyz
There is no no version.
See clear ip prefix-tree.
Chapter 1: Configuring Routing Policy
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