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IPv6 transition mechanisms
4in6 Tunneling from IPv4 to IPv6
6in4 Tunneling from IPv6 to IPv4
6over4 Transport of IPv6 data packets between dual-stack nodes over an IPv4 network
6to4 Transport of IPv6 data packets over an IPv4 network (obsolete)
AYIYA Anything In Anything
Dual stack Network nodes with IPv4 and IPv6 in parallel operation
Dual-Stack Lite (DS-Lite) Like dual stack, but with global IPv6 and carrier NAT IPv4
6rd IPv6 rapid deployment
ISATAP Intra-Site Automatic Tunnel Addressing Protocol (deprecated)
Teredo Encapsulation of IPv6 packets in IPv4 UDP -Datenpaketen
NAT64 Translation of IPv4 addresses into IPv6 addresses
464XLAT Translation from IPv4 to IPv6 to IPv4 addresses
SIIT Stateless IP / ICMP translation

464XLAT is an IPV4-IPv6-IPv4 translation method for use in pure IPv6 networks, for example for mobile communications - Internet service providers .


464XLAT described in RFC 6877 allows computers in IPv6 - networks to access Internet services that only via IPv4 can be reached.

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

Illustration for 464XLAT

The SIIT translation (CLAT) can be done directly on the client itself with special software or on an IPv4-capable (W) LAN in front of it, for example a smartphone in hotspot or tethering mode . However, if the LAN itself is connected via IPv4, 464XLAT is not necessary. The NAT64 translator must be able to reach the server and client (via CLAT).

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

There are (were) CLAT implementations for Android , the Nokia N900 and Windows Phone as well as Windows 10 (since 1703). Under Linux , clatd based on tayga or Jool CLAT can be implemented. PLAT does not differ from NAT64 and therefore does not require any further measures on the provider side.

The following table summarizes what has been sketched in the graphic by color-coded parcel routes:

Program and own host Target (server, other host) Translation of the IP packets Place of translation (s) Representation in the graphic
IPv4 IPv4 464XLAT (twice) CLAT and PLAT Red line
IPv4 IPv6 - - -
IPv6 IPv4 NAT64 / DNS64 (once) PLAT blue line
IPv6 IPv6 End-to-end IPv6 (without translation) - green line

Advantages and disadvantages

Since the 464XLAT is a supplement to NAT64 with DNS64, its advantages and disadvantages essentially also apply to 464XLAT. In contrast to NAT64, 464XLAT also works with services that are restricted to IPv4 addresses (for example URIs with numeric IPv4 addresses instead of names or software with outdated programming interfaces restricted to IPv4 ).

An additional disadvantage compared to NAT64 with DNS64 is the need for an additional service on the client or on the network in front of it (for example on the router). In addition, problems arise from replacing the usually 20-byte IPv4 header of a data packet with a 40-byte IPv6 header. A data packet grows by 20 bytes, which can lead to the maximum transmission unit being exceeded. Solutions such as Path MTU Discovery , IP fragmentation or MSS clamping become necessary.

464XLAT can solve problems ( RFC 6147 ) that can arise in DNS64 / NAT64 with the violation of DNSSEC through the use of synthetic unsigned AAAA records by using the signed A record, i.e. the IPv4 address. This case only occurs if a server only supports DNSSEC but not IPv6 and the client wants to do the validation. With a validation already in the DNS64 resolver / cache, the problem is solved even without the 464XLAT.

Practical use

Although 464XLAT can theoretically be used in any network that has no IPv4 but an IPv6 connection, the main focus of the application is on Internet access via cellular networks. Deutsche Telekom currently uses 464XLAT on current Android smartphones. Another example from Germany is the still experimentally rated WLAN operated by the LRZ with the SSID eduroam-IPv6only at the Munich universities.

IPv6 / NAT64 / DNS64 / 464XLAT is in the preparatory phase for many European mobile network providers. Deutsche Telekom (mobile network) started offering IPv6 in dual stack mode in parallel with IPv4 in summer 2015, Vodafone (mobile network) followed in November 2019.

In the summer of 2018, a user test took place at Deutsche Telekom on exclusive IPv6 operation. This test was successfully completed and put into regular operation on January 29, 2020.


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): address translator at the customer's ( stateless )

464 results from the double translation of 4 to 6 and 6 to 4

Individual evidence

  1. https://sites.google.com/site/tmoipv6/464xlat 464XLAT - A Solution for Providing IPv4 Services Over and IPv6-only Network (A solution for the realization of IPv4 services over IPv6 networks)
  2. http://code.google.com/p/n900ipv6/wiki/Nat64D
  3. https://web.archive.org/web/20150618223621/https://dev.windowsphone.com/en-US/OEM/docs/Customization/Additional_Internet_APN_settings
  4. https://web.archive.org/web/20170716194211/https://blogs.technet.microsoft.com/networking/2017/07/13/core-network-stack-features-in-the-creators-update -for-windows-10 /
  5. https://github.com/toreanderson/clatd CLATD Daemon for automatic configuration of CLAT under Linux
  6. http://www.litech.org/tayga/ NAT64 for Linux
  7. https://jool.mx/en/464xlat.html
  8. Johannes Spanier, Vodafone GmbH: 464XLAT Trial in an IPv6-only cellular network. (PDF) IPv6 Congress 2014, May 23, 2014, accessed on August 22, 2014 (presentation for the 2014 IPv6 Congress by heise Netze, iX and DE-CIX).
  9. https://www.lrz.de/services/netz/ipv6/
  10. https://www.heise.de/newsticker/meldung/IPv4-Daemmerung-Telekom-testet-IPv6-only-Kommunikation-im-Mobilfunk-4150047.html
  11. https://telekomhilft.telekom.de/t5/Blog/Neuer-IPv6-Zugang-zum-mobilen-Internet-im-Netz-der-Telekom/ba-p/4254741
  12. RFC 7915