A shared bridge domain across sites
VPLS connects multiple customer attachment circuits as one emulated Ethernet LAN. A PE learns source MAC addresses from local attachment circuits and received pseudowire traffic. It forwards known unicast toward the learned destination and can flood broadcast, unknown unicast and multicast within the service.
In a classic full-mesh VPLS, a PE does not forward frames from one core pseudowire to another in the same mesh. That split-horizon rule prevents the mesh from reflecting flooded frames back around the service.
VPLS signaling and EVPN MAC reachability
VPLS specifications describe both LDP signaling and BGP-based discovery and signaling. They establish service connectivity, and classic VPLS learns customer MACs from data traffic. EVPN distributes MAC reachability in BGP and adds control-plane mechanisms for features such as multihoming and MAC mobility.
Try it in a lab
- On three VPLS-capable PEs, attach one customer host at each site in the same bridge domain. Use host addresses in the same subnet.
- Send an ARP request from the first site. Confirm it reaches the other sites, then inspect the learned MAC table and verify that a later known unicast frame goes only toward its destination site.
- Check that a flooded frame received from a core pseudowire is not sent back into the same pseudowire mesh.