A broadband network gateway, BNG, in a wireline network, wherein the BNG has an interworking function in the control plane, IF-CP, and an interworking function in the user plane, IF-UP, wherein the IF-CP uses a control plane interface (N1'/N2') between the BNG and a 5G core in a 5G network to couple the control plane of the BNG to the control plane of the 5G core, and the IF-UP uses a user plane interface (N3') between the BNG and the 5G core to couple the user plane of the BNG to the user plane of the 5G core, the BNG comprising a memory containing instructions; a processor coupled to the memory, the processor configured to execute the instructions to cause the BNG to: transmit a registration request to the 5G core in a wireless network to register a residential gateway, coupled to an access node, which is then coupled to the BNG, the registration request containing a temporary identifier corresponding to the residential gateway in the wireline network, wherein the registration request indicates that the residential gateway has already been authenticated by the BNG; transmit a session establishment request to the 5G core, wherein the session establishment request comprises a tunnel endpoint identifier for the BNG; receive, from the 5G core, a session acknowledgement and establish a session, the session acknowledgement carrying a tunnel endpoint identifier of a user plane function in the 5G core; and send data packets toward the 5G core, after a tunnel between the BNG and the 5G network is established. a memory containing instructions; a processor coupled to the memory, the processor configured to execute the instructions to cause the BNG to: transmit a registration request to the 5G core in a wireless network to register a residential gateway, coupled to an access node, which is then coupled to the BNG, the registration request containing a temporary identifier corresponding to the residential gateway in the wireline network, wherein the registration request indicates that the residential gateway has already been authenticated by the BNG; transmit a session establishment request to the 5G core, wherein the session establishment request comprises a tunnel endpoint identifier for the BNG; receive, from the 5G core, a session acknowledgement and establish a session, the session acknowledgement carrying a tunnel endpoint identifier of a user plane function in the 5G core; and send data packets toward the 5G core, after a tunnel between the BNG and the 5G network is established. transmit a registration request to the 5G core in a wireless network to register a residential gateway, coupled to an access node, which is then coupled to the BNG, the registration request containing a temporary identifier corresponding to the residential gateway in the wireline network, wherein the registration request indicates that the residential gateway has already been authenticated by the BNG; transmit a session establishment request to the 5G core, wherein the session establishment request comprises a tunnel endpoint identifier for the BNG; receive, from the 5G core, a session acknowledgement and establish a session, the session acknowledgement carrying a tunnel endpoint identifier of a user plane function in the 5G core; and send data packets toward the 5G core, after a tunnel between the BNG and the 5G network is established.