The method includes the following steps. First, a controller receives a data packet that is reported by a switch connected to a source host; then the controller searches a local media access control (MAC) address table of physical addresses of devices to determine whether a destination address of the data packet exists, and the controller acquires a destination port if no destination address of the data packet exists, where the destination port is a port of a switch connected to a destination host, and the destination host is another host different from the source host; and finally, the controller uses the destination port as a destination address to generate a routing table, and sends the routing table to the switch connected to the source host, so that the switch connected to the source host forwards the data packet according to the routing table.