Techniques for determination of endpoint Internet Protocol (IP) address assignment in an Internet telephony system are disclosed. In conjunction with the establishment of a voice path between an endpoint and a gatekeeper in the Internet telephony system, a virtual address assigned to the endpoint in a network address translation operation is determined. The virtual address is then communicated to the endpoint as part of or otherwise in conjunction with a registration process prior to establishment of the voice path such that the registration process can complete successfully despite the network address translation operation. Advantageously, the invention overcomes problems associated with voice path registration failures resulting from network address translation in a router, virtual private network (VPN) gateway or other similar network address translation device.