A packet transmission method, a device, and a communications system, where the method includes receiving, by a forwarding plane apparatus, a media access control (MAC) address request broadcast by a base station, where the MAC address request includes a target Internet Protocol (IP) address and is used to request a MAC address corresponding to the target IP address, forwarding the MAC address request to a control plane apparatus when the forwarding plane apparatus does not save a first correspondence between the target IP address and the MAC address, receiving, the MAC address request response, and forwarding the MAC address request response to the base station.