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policy (Aggregate and Generated Routes)

 

Syntax

Hierarchy Level

Release Information

Statement introduced before Junos OS Release 7.4.

Statement introduced in Junos OS Release 9.0 for EX Series switches.

Statement introduced in Junos OS Release 11.3 for the QFX Series.

Statement introduced in Junos OS Release 12.3 for ACX Series routers.

Statement introduced in Junos OS Release 14.1X53-D20 for the OCX Series.

Description

Associate a routing policy when configuring an aggregate or generated route’s destination prefix in the routes part of the aggregate or generate statement. This provides the equivalent of an import routing policy filter for the destination prefix. That is, each potential contributor to an aggregate route, along with any aggregate options, is passed through the policy filter. The policy then can accept or reject the route as a contributor to the aggregate route.

If the contributor is accepted, the policy can modify the default preferences. The contributor with the numerically smallest prefix becomes the most preferred, or primary, contributor. A rejected contributor still can contribute to a less specific aggregate route. If you do not specify a policy filter, all candidate routes contribute to an aggregate route.

The following algorithm is used to compare two generated contributing routes in order to determine which one is the primary or preferred contributor:

  1. Compare the protocol’s preference of the contributing routes. The lower the preference, the better the route. This is similar to the comparison that is done while determining the best route for the routing table.

  2. Compare the protocol’s preference2 of the contributing routes. The lower preference2 value is better. If only one route has preference2, then this route is preferred.

  3. The preference values are the same. Proceed with a numerical comparison of the prefixes’ values.

    1. The primary contributor is the numerically smallest prefix value.

    2. If the two prefixes are numerically equal, the primary contributor is the route that has the smallest prefix length value.

At this point, the two routes are the same. The primary contributor does not change. An additional next hop is available for the existing primary contributor.

A rejected contributor still can contribute to less specific generated route. If you do not specify a policy filter, all candidate routes contribute to a generated route.

Options

policy-name—Name of a routing policy.

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.