IPv6 Essentials

Network Address and Protocol Translation

Address and protocol translation techniques are described in RFCs 2765 and 2766. They offer transition mechanisms in addition to dual-stack and tunneling techniques. The goal is to provide transparent routing for nodes in IPv6 networks to communicate with nodes in IPv4 networks and vice versa. The NAT gateway uses a pool of globally unique IPv4 addresses and binds them to IPv6 addresses. No changes to the end nodes are necessary.

The following abbreviations are used in RFC 2766 and throughout this section:

Network Address Translation (NAT)

Translates IP address, IP, TCP, UDP, and ICMP header checksums.

Network Address Port Translation (NAPT)

In addition to the fields translated by NAT transport, identifiers such as TCP and UDP port numbers and ICMP message types are translated.

Network Address Translation and Protocol Translation (NAT-PT)

Translates an IPv6 packet into an equivalent IPv4 packet and vice versa.

Network Address Port Translation and Protocol Translation (NAPT-PT)

Allows IPv6 hosts to communicate with IPv4 hosts using a single IPv4 address.

These concepts are explained in the following sections.

NAT

NAT has widely been used, especially to overcome the limitations of IPv4 address space. Corporate networks use IPv4 addresses from the private range and a NAT router at the border of the corporate network translates the private addresses to a single or a limited number of public addresses. NAT,as described here, provides routing ...