A gateway receives a link state packet (LSP) that includes a network identifier of a Layer 2 virtual network and a multicast address and that is sent by each routing bridge (RB) that is on the Transparent Interconnection of Lots of Links (TRILL) network; separately performs calculation on the network identifier and the multicast address that are in each LSP, to obtain a calculation result corresponding to each combination of the network identifier and the multicast address; if the gateway determines that information preconfigured on the gateway matches a calculation result corresponding to a combination of the network identifier and the multicast address, sends a notification message including the network identifier and the multicast address that are in the matched combination to each RB; receives from at least one RB, a multicast packet corresponding to the multicast address in the matched combination, and forwards the multicast packet.