METHOD OF FORWARDING MULTICAST DATA PACKET

A method, device and system for forwarding a multicast data packet are provided. The system is an extended bridge constructed by a controlling bridge and a port extender. The controlling bridge transmits a multicast data packet with an ETAG having a multicast ECID via a cascade port, and the multicast ECID directs to egress ports in different VLANs of the multicast group on a port extender connected with the cascade port. The port extender receives the packet with the ETAG via an upstream port connected with the controlling bridge, searches for multicast duplication information matching the multicast ECID, duplicates the packet for each egress port based on the multicast duplication information, removes the ETAG of each copy of the packet, adds a port identification and a VLAN identification of each egress port to each copy of the packet, and transmits the packet containing the VLAN identification via each egress port.