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Route Map Configuration Example
Copyright © 2010, Juniper Networks, Inc.
any order. If you do not specify any match conditions in a route map, that route map
matches all routes.
Set clauses define how the attributes are modified for matching routes. The set conditions
apply only to routes that pass all the match conditions (or a route map with no match
conditions). When a route passes all the match conditions, the router software applies
all set conditions. You issue set commands to define the set conditions for a route map.
You assign a unique string called the map tag to identify each route map. You can have
multiple instances of a route map, where each instance consists of a different group of
clauses. Each instance is identified by a sequence number. When you apply a route map,
the routing protocol evaluates routes against the instance of the route map with the
lowest sequence number. If the routes pass all the match conditions specified in the
lowest-numbered instance, and if all set commands are successfully applied, no other
instance of the route map is considered. However, any routes that do not pass all the
match conditions are evaluated against the next instance of the route map. For example,
suppose you create two instances of route map boston5, one with sequence number 10
and one with sequence number 25. When you apply boston5, routes are evaluated first
against instance 10; any that do not match are evaluated against instance 25.
When you apply a route map, you specify the permit or deny keyword:
If you specify the permit keyword, routes that match the route map are accepted,
forwarded, or redistributed. Routes that do not match the route map are rejected or
blocked.
If you specify the deny keyword, routes that match the route map are rejected or
blocked. Routes that do not match the route map are accepted, forwarded, or
redistributed.
A route map must have at least one match clause or one set clause. If you have no match
clauses, all routes match the route map, and the set conditions apply to all routes. If you
have no set clauses, no action is taken other than that specified by the permit or deny
keyword.
Consider the network structure shown in Figure 1 on page 6. Suppose you do not want
router Boston to receive any routes that originate in or pass through router Chicago.
Chapter 1: Configuring Routing Policy
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