Manual:BGP based VPLS

Overview

MPLSVPLS page covers general introduction to VPLS service and configuration of LDP based VPLS tunnels. Due to their static nature LDP based VPLS tunnels have scalability issues that arise when number of VPLSes and sites participating in VPLSes grow. One of the problems is the requirement to maintan full mesh of LDP tunnels between sites forming VPLS. In case number of sites in VPLS is high, adding new site to existing VPLS can become burdensome for network administrator.

BGP based autodiscovery and signaling of VPLS tunnels can help to avoid complexity of configuration at the expense of running BGP protocol between VPLS routers. In general, BGP based VPLS serves two purposes:

• autodiscovery: there is no need to configure each VPLS router with all remote endpoints of VPLS tunnels, provided there are means to deliver BGP multiprotocol NLRIs between them - routers figure out remote endpoints of tunnels from received BGP Updates;
• signaling: labels used for VPLS tunnels by remote endpoints are distributed in the same BGP Updates, this means there is no need for targeted LDP sessions between tunnel endpoints as in case of LDP signaled VPLS.

The drawback of running BGP based VPLS is requirement to configure BGP which requires that network administrator has at least basic understanding of BGP and its multiprotocol capabilities. Therefore it is advised to implement LDP signaled VPLS if amount of sites and VPLS networks are small.

BGP based VPLS is documented in RFC 4761.