In an environment that is using BGP signaling to establish L2VPNs, the MPLS Topology Server creates a VRF instance and a RouteTarget instance for each discovered VRF and route target that are associated with the L2VPN. BGP-signaled L2VPNs not only use BGP signaling to construct, advertise, maintain, and delete pseudowires, but also use BGP and route targets to discover all the VRFs that belong to an L2VPN.
In a BGP-signaled VPLS, the route target is the same for the VPLS across all VRFs/PEs that belong to the VPLS. The route target is the VPLS ID for a BGP-signaled VPLS.
As with the discovery and modeling of L3VPNs, the MPLS Topology Server relates VRFs and RouteTargets through the Imports/ImportedBy and Exports/ExportedBy relationship sets, and then discovers which interfaces are associated with each VRF. By matching the VRF interfaces to the ForwarderEndpoint interfaces, the MPLS Topology Server discovers which Forwarders, ForwarderEndpoints, and PseudoWires are part of a VPN.
“VRF and RouteTarget” on page 115 describes additional relationships that are created for VRFs and RouteTargets.