Broadcast Storms Ahead! What Happens When You Skip Split Horizon in VPLS
Overview Virtual Private LAN Service is a Layer 2 VPN technology that lets business sites scattered across the globe appear as if they're connected on the same local Ethernet network. Built over an MPLS or IP backbone, VPLS creates a virtual Ethernet switch across provider edge routers. That lets customer edge devices talk to each other directly over Ethernet frames. Signaling protocols like LDP or BGP help PE routers set up pseudo wires—those are the tunnels that carry Layer 2 frames. The routers also learn MAC addresses dynamically to forward unicast traffic. They flood broadcast and multicast frames as needed. That setup is perfect for enterprises that need seamless Layer 2 connectivity across locations for services like VoIP, video conferencing or legacy systems. But without proper configuration—like split horizon groups—VPLS can run into loops and broadcast storms. That makes precise setup critical to its success. Split Horizon Group A split horizon group is a loop pr...