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IPv6 NAT-PT Communication Overview

NAT-PT communication with static mapping— Network Address Translation-Protocol Translation (NAT-PT) can be done in two directions, from IPv6 to IPv4 and vice versa. For each direction, static NAT is used to map the destination host to a local address and a source address NAT is used to translate the source address. There are two types of static NAT and source NAT mapping: one-to-one mapping and prefix-based mapping.

NAT- PT communication with DNS ALG—A DNS-based mechanism dynamically maps IPv6 addresses to IPv4-only servers. NAT-PT uses the DNS ALG to transparently do the translations. For example, a company using an internal IPv6 network needs to be able to communicate with external IPv4 servers that do not yet have IPv6 addresses.

To support the dynamic address binding, a DNS should be used for name resolution. The IPv4 host looks up the name of the IPv6 node in its local configured IPv4 DNS server, which then passes the query to the IPv6 DNS server through a device using NAT-PT.

The DNS ALG in NAT device :

  • Translates the IPv6 address resolution back to IPv4 address resolution.

  • Allocates an IPv6 address for the mapping.

  • Stores a mapping of the allocated IPv4 address to the IPv6 address returned in the IPv6 address resolution so that the session can be established from any-IPv4 hosts to the IPv6 host.