A method and gateway obtain a route according to a requirement. The method includes: a first gateway receives a first packet; the first gateway searches a forwarding table for a next hop of a first IP address in the first packet, wherein the search fails; the first gateway sends a second packet carrying the first IP address to at least one gateway; the first gateway receives a third packet from a second gateway; and the first gateway writes an address of the second gateway into the forwarding table as a next hop address of the first IP address.