A data packet transmission method, comprising: receiving (S201), by a first border routing bridge device of a first area, a first data packet sent by a border routing bridge device of a second area to the first area, wherein the first data packet comprises: a device identifier of the border routing bridge device of the second area that is used as a source routing bridge device identifier, a device identifier of the first border routing bridge device that is used as a target routing bridge device identifier, a device identifier of a source device, and a device identifier of a target device; determining (S202), by the first border routing bridge device, a device identifier group of the second area according to the first data packet, wherein the device identifier group of the second area comprises device identifiers of all border routing bridge devices of the second area; determining (S203), by the first border routing bridge device, one border routing bridge device identifier from the device identifier group of the second area according to the first data packet, wherein the determined border routing bridge device identifier identifies a border routing bridge device of the second area, and the border routing bridge device is used to forward a return data packet sent by the target device to the source device; and sending (S204), by the first border routing bridge device, a second data packet that carries the determined border routing bridge device identifier to the target device, wherein the determined border routing bridge device identifier is used as a source routing bridge device identifier of the second data packet. receiving (S201), by a first border routing bridge device of a first area, a first data packet sent by a border routing bridge device of a second area to the first area, wherein the first data packet comprises: a device identifier of the border routing bridge device of the second area that is used as a source routing bridge device identifier, a device identifier of the first border routing bridge device that is used as a target routing bridge device identifier, a device identifier of a source device, and a device identifier of a target device; determining (S202), by the first border routing bridge device, a device identifier group of the second area according to the first data packet, wherein the device identifier group of the second area comprises device identifiers of all border routing bridge devices of the second area; determining (S203), by the first border routing bridge device, one border routing bridge device identifier from the device identifier group of the second area according to the first data packet, wherein the determined border routing bridge device identifier identifies a border routing bridge device of the second area, and the border routing bridge device is used to forward a return data packet sent by the target device to the source device; and sending (S204), by the first border routing bridge device, a second data packet that carries the determined border routing bridge device identifier to the target device, wherein the determined border routing bridge device identifier is used as a source routing bridge device identifier of the second data packet. <EOS>