The US Department of Defense (DoD) plans to add Internet protocol (IP) version 6 (IPv6) capability to all DoD IP networks by 2008 then begin a phase-out of IP version 4 (IPv4). To facilitate this migration various transition mechanisms have been developed to address interoperability of IPv4 and IPv6 networks and systems. Unfortunately, none of the existing mechanisms address two fundamental problems: (1) noninvasive migration of essential legacy IPv4-only systems to IPv6, and (2) operation of IPv4-only systems on IPv6-only core networks. This paper presents a solution to these problems by using a simple, low cost IPv4/IPv6 proxy translation device