An approach is provided for supporting integrated voice and data services over a common Session Initiation Protocol (SIP)-based Customer Premise Equipment (CPE) device. The device includes a network interface that receives a call from a calling party device to a called party device. Also, the device has signaling conversion logic configured to convert between Session Initation Protocol (SIP) signaling and circuit-switched telephony signaling to support the call, wherein addressing information of the calling party device is preserved in the conversion. The called party device includes one of a telephone station and a SIP client. The device further includes a voice port coupled to the signaling conversion logic and configured to communicate selectively with the telephone station; and a data port configured to communicate selectively with the SIP client.