BGP multiprotocol extensions (MP-BGP) enable BGP
to support IPv4 services such as BGP/MPLS VPNs, which are sometimes
known as RFC 2547bis VPNs. VPLS with BGP signaling is actually a BGP-MPLS
application that has much in common with BGP/MPLS VPNs.
The procedures for configuring BGP signaling for
BGP/MPLS VPNs and for VPLS are similar except, for VPLS, you must
configure both of the following BGP address families:
L2VPN—The L2VPN address family enables you to configure
the PE router for VPLS (or VPWS) L2VPNs to exchange layer 2 network
layer reachability information (NLRI) for all VPLS (or VPWS) instances.
Optionally, you can use the signaling keyword
with the address-family command for the
L2VPN address family to specify BGP signaling of VPLS reachability
information. Currently, you can omit the signaling keyword with no adverse effects.
VPLS—The VPLS address family enables you to configure
the PE router to exchange layer 2 NLRI for a specified VPLS instance.
BGP can exchange information in a VPLS topology
within these address families. Specifically, BGP builds a full mesh
of label-switched paths (LSPs) among all of the VPLS instances on
each of the PE routers participating in a particular VPLS domain.