Cross-network-segment discovery method and system, and routing device

A cross-network-segment discovery method, wherein the method is applied to a first routing device, a second routing device, a first electronic device, and a second electronic device;

• the first routing device, the first electronic device, and the second electronic device are located in a first area;
• the second routing device is located in a second area;
• the first electronic device and the second electronic device connect to the first routing device;
• the first routing device and the second routing device connect to a same local area network;
• the first routing device and the second routing device provide different network segments;
• and the method comprises:
• sending, by the first electronic device, a digital living network alliance DLNA delivery request message to the second electronic device, wherein the DLNA delivery request message comprises at least one URL and an identifier of the second electronic device;
• displaying or playing, by the second electronic device, content corresponding to the URL after receiving the DLNA delivery request message;
• after the first electronic device moves from the first area to the second area, disconnecting, by the first electronic device, from the first routing device, and connecting to the second routing device;
• sending, by the first electronic device, a first request message to the second routing device, wherein the first request message comprises a fixed multicast address;
• forwarding, by the second routing device, the first request message to the first routing device after receiving the first request message;
• sending, by the first routing device, the first request message in a multicast mode within a range of a first multicast address after receiving the first request message;
• after receiving the first request message, sending, by the second electronic device, a first response message to the first electronic device through the first routing device and the second routing device in sequence;
• and
• receiving the first response message, and discovering, by the first electronic device, the second electronic device.