Interconnection method for interconnecting first and second sub-networks, the said first sub-network being a local network on which is connected an internet gateway linking the said first sub-network to a third sub-network, the said second sub-network being a femto-cell, the said first and second sub-networks being adapted to allow UPnP devices (130; 140) to be connected thereto, each UPnP device comprising at least one server associated with an IP address and a port number, the method being such that an interconnection device interconnecting the said first and second sub-networks performs the following prior steps when the interconnection device detects the presence of a UPnP mobile terminal in the femto-cell: - subscribing, on each of the first and second sub-networks, to a predefined IP address and a predefined port number to which are addressed multicast UDP datagrams transmitted during a UPnP discovery phase, and - starting to listen for UDP datagrams transmitted to the said IP address of the interconnection device and the port number allocated by the interconnection device to the said server; then; following the implementation of the prior steps, the interconnection device performs: - determining (303; 309; 409), for the said first and second sub-networks, actual IP addresses and port numbers of servers of UPnP devices; - allocating a port number to each of the said servers; - establishing, on receipt of a connection request corresponding to a port number allocated by the interconnection device to a said server, a connection between the interconnection device and the said server, and a connection between the interconnection device and the UPnP device that emitted the said request; and in at least one frame, received by the interconnection device via one of the said connections: - replacing in the said frame each actual IP address and actual port number of a server belonging to the sub-network of emission of the said frame with an IP address of the interconnection device, usable to route the data over the other sub-network than that to which the said server is connected from among the said first and second sub-networks, and the port number allocated by the interconnection device to the said server, and - replacing in the said frame each IP address of the interconnection device usable on the sub-network of emission of the said frame and port number allocated by the interconnection device to a server with the IP address and the port number of the corresponding server; and - transmitting the said frame thus modified on a sub-network chosen from among the first and second sub-networks, the sub-network chosen being that through which the interconnection device has not received the said frame. - subscribing, on each of the first and second sub-networks, to a predefined IP address and a predefined port number to which are addressed multicast UDP datagrams transmitted during a UPnP discovery phase, and - starting to listen for UDP datagrams transmitted to the said IP address of the interconnection device and the port number allocated by the interconnection device to the said server; - determining (303; 309; 409), for the said first and second sub-networks, actual IP addresses and port numbers of servers of UPnP devices; - allocating a port number to each of the said servers; - establishing, on receipt of a connection request corresponding to a port number allocated by the interconnection device to a said server, a connection between the interconnection device and the said server, and a connection between the interconnection device and the UPnP device that emitted the said request; - replacing in the said frame each actual IP address and actual port number of a server belonging to the sub-network of emission of the said frame with an IP address of the interconnection device, usable to route the data over the other sub-network than that to which the said server is connected from among the said first and second sub-networks, and the port number allocated by the interconnection device to the said server, and - replacing in the said frame each IP address of the interconnection device usable on the sub-network of emission of the said frame and port number allocated by the interconnection device to a server with the IP address and the port number of the corresponding server; and - transmitting the said frame thus modified on a sub-network chosen from among the first and second sub-networks, the sub-network chosen being that through which the interconnection device has not received the said frame.