Abstract
3 Abstract Nowadays, people have largely suffered the insufficient IP address, which can be found in schools, companies, and enterprises; therefore, some people come up with the NAT system to solve this problem. However, it is very limited for application to pass through the NAT, and divides the Internet into public and private, which disobeys the basic sharing principle. For this reason, IETF proposes the IPV6, the brand new protocol, and the sound Internet system; above all, more IP addresses can completely solve the difficulty we face in the field of the Internet. As we all know that it is difficult to translate from the IPV4 to the IPV6 on Internet because most users don’t want to change the status quo; hence, the perfect solution is to make users unconscious for the transitional process. So more and more translation mechanisms are proposed, and among them the NAT-PT, the translator, is very mature and implemented by every kind of machine, especially, users cannot be unaware of the process of transition. NAT-PT still can’t overcome the problem of the inadequate addresses, so for the purpose of solving this question, IETF proposes NAPT-PT, adding port translation to NAT-PT, like that, one IPv4 address can map to multi-IPv6 addresses. But the NAPT-PT in RFC 2766 only can translate packet from the IPv6 domain to the IPv4 domain, it is not usable for Internet. This thesis makes the manufacture of NAPT-PT more complete, reaching the bi-directional communications and is implemented on the LINUX.