BGP Path Selection for Layer 2 VPNs and VPLS

By default, Juniper Networks routers use just the designated forwarder path selection algorithm to select the best path to reach each Layer 2 VPN or VPLS routing instance destination. However, you can now configure the routers in your network to use both the BGP path selection algorithm and the designated forwarder path selection algorithm. The Provider routers within the network can use the standard BGP path selection algorithm. Using the standard BGP path selection for Layer 2 VPN and VPLS routes allows a service provider to leverage the existing Layer 3 VPN network infrastructure to also support Layer 2 VPNs and VPLS. The BGP path selection algorithm also helps to ensure that the service provider's network behaves predictably with regard to Layer 2 VPN and VPLS path selection. This is particularly important in networks employing route reflectors and multihoming. The PE routers continue to use the designated forwarder path selection algorithm to select the preferred path to reach each CE device. The VPLS designated forwarder algorithm uses the D-bit, preference, and PE router identifier to determine which path to use to reach each CE device in the Layer 2 VPN or VPLS routing instance.