Embodiments of the present invention provide a data transmission method, a forwarding information update method, a communications device, and a controller. The communications device includes: a forwarding module and one or more interfaces, where the forwarding module receives a data packet sent to a receive end; determines, according to a correspondence between data filtering template information of the data packet and interface information in forwarding information maintained by the forwarding module, an interface for forwarding the data packet to the receive end, where if data packet transmission is performed by using a specific radio access technology between the communications device and a next hop to which the communications device forwards the data packet, the interface is an interface corresponding to the radio access technology; and forwards the data packet to the interface; and the interface receives the data packet sent by the forwarding module, and forwards the data packet.