Layer 2 protocol tunneling allows Layer 2 devices to use Layer 2 tunneling technology to transparently transmit Layer 2 protocol data units (PDUs) across a Layer 2 network. Layer 2 protocol tunneling supports standard protocols, such as Spanning Tree Protocol (STP), Link Aggregation Control Protocol (LACP), as well as user-defined protocols.
Layer 2 protocol tunneling ensures transparent transmission of private Layer 2 PDUs over a public network. The ingress device replaces the multicast destination MAC address in the received Layer 2 PDUs with a specified multicast MAC address before transmitting them onto the public network. The egress device restores the original multicast destination MAC address and then forwards the Layer 2 PDUs to their destinations.