A gateway device receives interface information sent by an interface extension device, where an Ethernet interface of the interface extension device is connected to a target Ethernet interface of the gateway device, and the interface information includes an interface type and a media access control (MAC) address of a first non-Ethernet interface of the interface extension device. The gateway device creates a first virtual interface on the target Ethernet interface based on the interface information, where the first virtual interface corresponds to the first non-Ethernet interface, and an interface type of the first virtual interface is an Ethernet interface. The gateway device sends an interface creation success notification to the interface extension device. The gateway device may obtain data of the first non-Ethernet interface through the first virtual interface, thereby implementing interface extension of the gateway device.