Definition of Route Targets for VRFs Overview

BGP uses an extended-community attribute, the route target, to filter appropriate VPN routes into the correct VRFs. You configure the export list on the VRF to specify export route targets. When BGP advertises a route from this VRF’s forwarding table, it associates the list of export route targets with the route and includes this attribute in the update message that advertises the route.

You also configure a route-target import list on each VRF to specify import route targets. When a PE router receives a route, BGP compares the route target list associated with the route (and carried in the update message) with the import list associated with each VRF configured in the PE router.

An export list defines a route-target extended community. Routes having any route target in their export list that matches a route target in a VRF’s import list are installed in the VRF’s forwarding table.

An import list defines a route-target extended community. Only routes that have at least one matching route target in their associated export list can be installed into the VRF’s forwarding table.

If the import and export lists are identical, use the both keyword to define both lists simultaneously.

You can add only one route target to a list at a time.

For VPN-IPv4 routes received from another PE router, if any route target in the export list matches a route target in a VRF’s import list, then the route is installed in that VRF’s forwarding table.

A route-target export list can be modified on the sending PE router by an export map or outbound routing policy. It can be modified on the receiving PE router by an import map or inbound routing policy.

Related Documentation