Interprovider VPNs—Configure MP-IBGP between AS Border Routers

In this approach, the PE routers within an AS use multiprotocol internal BGP (MP-IBGP) to distribute labeled VPN-Internet Protocol version 4 (IPv4) routes to an AS border router or a route reflector of which the AS border router is a client. The AS border router uses multiprotocol external BGP (MP-EBGP) to distribute the labeled VPN-IPv4 routes to its peer AS border router in the neighboring AS. The peer AS border router then uses MP-IBGP to distribute labeled VPN-IPv4 routes to PE routers, or to a route reflector of which the PE routers are a client.

This approach enhances the scalability of an EBGP VRF-to-VRF configuration because it eliminates the need to configure all of the VPNs on every AS border router. However, it also introduces some complexity:

• All the VRF routes must be stored in the AS border router.
• An LSP must be established from ingress PE routers to egress PE routers.
• Secure connections must exist among the ASs along the path from the ingress PE router to the egress PE router.
• The ASs must be configured to know which AS border routers receive routes with specific route target attributes.