A service forwarding method performed by a residential gateway, comprising: receiving a DHCP discover packet that comprises a service request and that is sent by a LAN-side device, wherein the DHCP discover packet comprises a DHCP Option field, the DHCP Option field comprises a first value, and the first value identifies a requested service; if the service identified by the value is corresponding to a bridged WAN port, forwarding, by the residential gateway, the DHCP discover packet from the bridged WAN port to a broadband access server,, receiving, by the residential gateway, a DHCP Offer response packet returned by the broadband access server, and recording a binding relationship between a source MAC address of the LAN-side device and the bridged WAN port; determining, by the residential gateway, a corresponding LAN port based on the binding relationship between the source MAC address of the LAN-side device and the bridged WAN port, and sending the DHCP Offer response packet to the LAN-side device by using the LAN port; and receiving, by the residential gateway, a DHCP request packet sent by the LAN-side device, and finding, by the residential gateway, the bridged WAN port based on the binding relationship between the source MAC address of the LAN-side device and the bridged WAN port; and establishing a link to the broadband access server by using the bridged WAN port; wherein establishing a link to the broadband access server by using the bridged WAN port comprises, sending the DHCP request packet to the broadband access server by using the bridged WAN port, and receiving a DHCP acknowledgement packet returned by the broadband access server; and sending, by the residential gateway, the DHCP acknowledgement packet to the LAN-side device by using the LAN port, wherein the DHCP acknowledgement packet comprises a public IP address, which is assigned by a DHCP server to the LAN-side device. receiving a DHCP discover packet that comprises a service request and that is sent by a LAN-side device, wherein the DHCP discover packet comprises a DHCP Option field, the DHCP Option field comprises a first value, and the first value identifies a requested service; if the service identified by the value is corresponding to a bridged WAN port, forwarding, by the residential gateway, the DHCP discover packet from the bridged WAN port to a broadband access server,, receiving, by the residential gateway, a DHCP Offer response packet returned by the broadband access server, and recording a binding relationship between a source MAC address of the LAN-side device and the bridged WAN port; determining, by the residential gateway, a corresponding LAN port based on the binding relationship between the source MAC address of the LAN-side device and the bridged WAN port, and sending the DHCP Offer response packet to the LAN-side device by using the LAN port; and receiving, by the residential gateway, a DHCP request packet sent by the LAN-side device, and finding, by the residential gateway, the bridged WAN port based on the binding relationship between the source MAC address of the LAN-side device and the bridged WAN port; and establishing a link to the broadband access server by using the bridged WAN port; wherein establishing a link to the broadband access server by using the bridged WAN port comprises, sending the DHCP request packet to the broadband access server by using the bridged WAN port, and receiving a DHCP acknowledgement packet returned by the broadband access server; and sending, by the residential gateway, the DHCP acknowledgement packet to the LAN-side device by using the LAN port, wherein the DHCP acknowledgement packet comprises a public IP address, which is assigned by a DHCP server to the LAN-side device.