Provided are methods of ensuring network continuity performed at a local gateway, a fixed gateway, and a network device. The method of ensuring network continuity performed at a local gateway includes establishing a tunnel with a fixed gateway serving as a relay between an Internet service server and the local gateway, and performing communication with the fixed gateway through the tunnel. Therefore, even when the type of an uplink signal received by a local gateway changes or the local gateway is in an uplink signal shadow area, a terminal connected to the local gateway can be provided with a seamless Internet service.