Configuring Static Route Target Filtering for VPNs

The BGP VPN route target extended community (RFC 4360, BGP Extended Communities Attribute) is used to determine VPN membership. Static route target filtering helps to prevent resources from being consumed in portions of the network where the VPN routes are not needed due to the lack of member PE routers (RFC 4684, Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)). Routers can originate routes into the RT-Constrain protocol to indicate their interest in receiving VPN routes containing route targets that match the RT-Constrain NLRI.