Table of Contents
Advertisement
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:
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.
Route Map Configuration Example
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.
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.
Chapter 1: Configuring Routing Policy
Route Maps
5
Advertisement
Table of Contents
