# Overview

Routing policy determines how the system handles the routes it receives from and sends to neighboring routers. In many cases, routing policy consists of the following:

- Filtering routes
- Accepting certain routes
- Accepting and modifying other routes
- Rejecting some routes
- Determining the routing protocol used to distribute the routes

You can think of routing policy as a way to control the flow of routes into and out of the router.

The decision about which routes to accept from and advertise to various neighbors has an important impact on the traffic that crosses a network. Routing policy is used to enforce business agreements between two or more Internet service providers (ISPs) concerning the amount and type of traffic that is allowed to pass between them.

You can use one or more of the following mechanisms to configure routing policy:

- Route Maps
- Match Policy Lists
- Access Lists
- Prefix Lists
- Prefix Trees
- Community Lists