Routing policies

Overview

Routing policies, also known as route redistribution policies, are used to make routing decisions based on policies that override the default routing protocol decisions. Normally, when a router receives a packet, where it is forwarded to is based on the destination address in the packet, which is then used to look up an entry in a routing table.

You may have a requirement to forward a packet based on other criteria to reach a destination. For example, you can selectively apply routing policies based on prefix and community access lists, packet size, advertised routes, the size and contents of the routing table, and other user-defined criteria. Additional user actions can also be applied to define user-defined routes, and to set the precedence, the type of service bits, and the damping method for the routes.

There are no default routing policies on the NFM-P. Each policy must be created and applied to an object, a routing protocol, or the forwarding table. Each set of rules that is associated with controlling routes are called routing policy statement entries on the client GUI. For example, use routing policies to:

• control routing protocols, such as BGP, to allow routes from another protocol, such as OSPF, into the routing table, which allows the routing table to redistribute packets into other protocols

• control the import and export of learned active routes of a protocol

• modify the characteristics of a route, for example, to change the community values of BGP AS path attributes

• prevent the routes for specific customers from being added to routing tables

• control BGP route flapping