IPv6 transition mechanisms#464XLAT

464XLAT is an IPv4 - IPv6 transition mechanism for use in pure IPv6 networks, such as wireless ISPs.


464XLAT described in RFC 6877 allows computers in IPv6 networks to access Internet services that are only reachable via IPv4, such as Skype.

The client uses a SIIT translator ( CLAT ) to convert IPv4 packets in IPv6. These packets are sent to a NAT64 translator ( PLAT ) and back -translated. You can then reach an IPv4 server.

The SIIT translation ( CLAT ) can be done directly on the client itself with special software or on an IPv4 -enabled LAN before. If the LAN is, however, itself connected via IPv4, 464XLAT is not necessary. The NAT64 translator needs to achieve ( through CLAT ) to be able to server and client.

The use of NAT64 limits connections to the client -server model with the protocols UDP, TCP and ICMP.

There CLAT implementations for Android and Nokia N900. Under Linux can be realized with clatd based on tayga CLAT. PLAT is no different from NAT64 and requires so on provider side no further action.

The following table summarizes again what was outlined in the graph by color-coded package way:

Pros and Cons


  • It will also work IPv4 services whose URLs contain numeric IPv4 addresses instead of names. The sole use of NAT64 with DNS64 is dependent on name via A record, which are supplemented by AAAA records.


  • It must be running before an additional service on the client or on the immediate network.
  • The connection must be made from the client, ie Server services are on the client side not possible, peer-to- peer is not.
  • Other disadvantages, which basically arise from address translations, would be additional.

Practical Application

Although 464XLAT can be theoretically used on networks that no IPv4 but has an IPv6 connection, the focus of the application in the Internet via mobile phone. Currently used T-Mobile USA 464XLAT on current Android smartphones.

For European mobile operators to IPv6/NAT64/DNS64/464XLAT is in the preparation phase.


SIIT Stateless IP / ICMP Translation: stateless translation of IP packets and ICMP packets from IPv4 to IPv6 and vice versa

PLAT provider- side translator ( XLAT ): address translator at the provider ( stateful )

CLAT customer -side translator ( XLAT ): at the customer's address translator ( stateless )

464 resulting from the two-time transmission from 4 to 6 and 6 to the 4