Nokia’s router supports two databases for routing information. The routing database is composed of the routing information learned by the routing protocols. The forwarding database is composed of the routes actually used to forward traffic through a router. In addition, link state databases are maintained by interior gateway protocols (IGPs) such as IS-IS and OSPF.
Routing protocols calculate the best route to each destination and place these routes in a forwarding table. The routes in the forwarding table are used to forward routing protocol traffic, sending advertisements to neighbors and peers.
A routing policy can be configured that will not place routes associated with a specific origin in the routing table. Those routes will not be used to forward data packets to the intended destinations and the routes are not advertised by the routing protocol to neighbors and peers.
Routing policies control the size and content of the routing tables, the routes that are advertised, and the best route to take to reach a destination. Careful planning is essential to implement route policies that can affect the flow of routing information or packets in and traversing through the router. Before configuring and applying a route policy, develop an overall plan and strategy to accomplish your intended routing actions.
There are no default route policies. Each policy must be created explicitly and applied to a routing protocol or to the forwarding table. Policy parameters are modifiable.