IPv6 is a new version protocol for next generation Internet, which has the advantages of supporting scalability, mobility and security better than current IPv4 Internet. However, IPv4 and IPv6 are not directly compatible. IPv4/IPv6 translator with high performance and reliability can facilitate the seamless coexistence of IPv4 and IPv6 networks during the transition period. In this paper, we proposed a design and implementation of IPv4/IPv6 translator using network processors. The challenges of this work lie in three areas: 1) effective use of network processor resources, 2) design and implementation of an advanced control plane on a commodity OS, and 3) fault tolerance to improve reliability of the Whole system. We discuss our solutions to these challenges and presented analytic models to investigate the fault tolerance issue of our approaches. Our work provided guidelines and insights into design, implementation and configuration of the IPv4/IPv6 translator.