A segment routing device receives a first packet from a first network. A first packet header of the first packet includes a segment list. The segment list includes a plurality of sequentially arranged identifiers. The identifiers include a first-type identifier and a plurality of second-type identifiers. Network devices or links identified by the first-type identifier and the second-type identifier are respectively on the first network and a second network. A type of the first network is different from a type of the second network. The segment routing device encapsulates a second packet header for the first packet to form a second packet. The second packet header includes the plurality of second-type identifiers. The segment routing device sends the second packet to the second network.