While IPv4 and IPv6 coexists in the current Internet, there are multiple transition mechanisms that provide IPv4 connectivity to or across IPv6 networks, and these mechanisms each usually requires its own specific Customer Premises Equipment (CPE) to function. In this article, we propose a specification whereby a single unified CPE can support multiple mainstream transition mechanisms, including Mapping of Address and Port (MAP-T, MAP-E), 464XLAT, Dual-Stack Lite (DS-Lite), and dual-stack. The unified CPE detects network configurations, and automatically adapts its functionalities.