L3VPN: Inter-AS: ASBR Option C

For the ASBR Option-C interprovider VPN solution, the customer service provider depends on the VPN service provider to deliver a VPN transport service between the customer service provider's points of presence (POPs) or regional networks. This functionality might be used by a VPN customer who has connections to several different service providers, or different connections to the same service provider in different geographic regions, each of which has a different autonomous system (AS) number. For option C, only routes internal to the service provider networks are announced between ASBRs. This is achieved by using the family inet labeled-unicast statements in the IBGP and EBGP configuration on the PE routers. Labeled IPv4 (not VPN-IPv4) routes are exchanged by the ASBRs to support MPLS. An MP-EBGP session between the end PE routers is used for the announcement of VPN-IPv4 routes. In this manner, VPN connectivity is provided while keeping VPN-IPv4 routes out of the core network.