Overview of Routing Policy

Definition

Routing policies are used to filter routes and set attributes for routes. Changing route attributes (including reachability) changes the path that network traffic passes through.

The difference between a routing policy and policy-based routing (PBR) is as follows:

• Routing policies apply to routes. Based on routing protocols, the result of route generation, advertisement, and selection is changed by following rules, changing parameters, or using control modes. That is, the contents in the routing table are changed.
• PBR applies to data packets. PBR provides a means to route or forward data packets flexibly based on predefined policies instead of following the routes in the existing routing table.

Objective

When advertising, receiving, and importing routes, the router implements certain policies based on actual networking requirements to filter routes and change the attributes of the routes. Routing policies serve the following purposes:

• Control route advertising

  Only routes that match the rules specified in a policy are advertised.

• Control route receiving

  Only the required and valid routes are received. This reduces the size of the routing table and improves network security.

• Filter and control imported routes

  A routing protocol may import routes discovered by other routing protocols. Only routes that satisfy certain conditions are imported to meet the requirements of the protocol.

• Modify attributes of specified routes

  Attributes of the routes that are filtered by a routing policy are modified to meet the requirements of the local device.

Benefits

This feature brings the following benefits:

• Controls the size of the routing table, saving system resources.
• Controls route receiving and advertising, improving network security.
• Modifies attributes of routes for proper traffic planning, improving network performance.