A method includes obtaining, by a first network node, a first segment identifier advertisement message, where the first segment identifier advertisement message includes a first segment identifier and a first flag bit, and the first segment identifier is corresponding to a second network node; determining, by the first network node, that the first flag bit indicates that a packet needs to be forwarded through the second network node; and generating, by the first network node, a first packet forwarding path, where the first packet forwarding path includes the second network node.