Policy Framework Configuration Guide - Juniper Networks

Junos 10.4 Policy Framework Configuration Guide
Including BGP Communities and Extended Communities in Routing Policy Match
Conditions
To include a BGP community or extended community in a routing policy match condition,
include the community condition in the from statement of a policy term:
from {
community [ names ];
}
You can include this statement at the following hierarchy levels:
• [edit policy-options policy-statement policy-name term term-name]
• [edit logical-systems logical-system-name policy-options policy-statement policy-name
term term-name]
Additionally, you can explicitly exclude BGP community information with a static route
by using the none option. Include this option when configuring an individual route in the
route portion to override a community option specified in the defaults portion.
NOTE: You can include the names of multiple communities in the community
match condition. If you do this, only one community needs to match for a
match to occur (matching is effectively a logical OR operation).
How BGP Communities and Extended Communities Are Evaluated in Routing Policy
Match Conditions
When you use BGP communities and extended communities as match conditions in a
routing policy, the policy framework software evaluates them as follows:
• Each route is evaluated against each named community in a routing policy from
statement. If a route matches one of the named communities in the from statement,
the evaluation of the current term continues. If a route does not match, the evaluation
of the current term ends.
• The route is evaluated against each member of a named community. The evaluation
of all members must be successful for the named community evaluation to be
successful.
• Each member in a named community is identified by either a literal community value
or a regular expression (for information about using regular expressions, see “Using
UNIX Regular Expressions in Community Names” on page 105). Each member is
evaluated against each community associated with the route. (Communities are an
unordered property of a route. For example, 1:2 3:4 is the same as 3:4 1:2.) Only one
community from the route is required to match for the member evaluation to be
successful.
• Community regular expressions are evaluated on a character-by-character basis. For
example, if a route contains community 1234:5678, the regular expressions see nine
110
Copyright © 2010, Juniper Networks, Inc.