Deprecation of "ip6.int"
Switch from ip6.int to ip6.arpa for IPv6 reverse DNS lookups
Huston, G., "Deprecation of "ip6.int"", BCP 109, RFC 4159, DOI 10.17487/RFC4159, August 2005, <https://www.rfc-editor.org/info/rfc4159>.
@misc{rfc4159,
series = {Request for Comments},
number = 4159,
howpublished = {RFC 4159},
publisher = {RFC Editor},
doi = {10.17487/RFC4159},
url = {https://www.rfc-editor.org/info/rfc4159},
author = {G. Huston},
title = {{Deprecation of "ip6.int"}},
pagetotal = 3,
year = 2005,
month = aug,
} RFC text
Contents
Network Working Group G. Huston
Request for Comments: 4159 APNIC
BCP: 109 August 2005
Category: Best Current Practice
Deprecation of "ip6.int"
Status of This Memo
This document specifies an Internet Best Current Practices for the
Internet Community, and requests discussion and suggestions for
improvements. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document advises of the deprecation of the use of "ip6.int" for
Standards Conformant IPv6 implementations.
1. IPv6 Standards Action
In August 2001 the IETF published [RFC3152], which advised that the
use of "ip6.int" as the domain for reverse-mapping of IPv6 addresses
to DNS names was deprecated. The document noted that the use of
"ip6.int" would be phased out in an orderly fashion.
As of 1 September 2005, the IETF advises the community that the DNS
domain "ip6.int" should no longer be used to perform reverse mapping
of IPv6 addresses to domain names, and that the domain "ip6.arpa"
should be used henceforth, in accordance with the IANA Considerations
described in [RFC3596]. The domain "ip6.int" is deprecated, and its
use in IPv6 implementations that conform to the IPv6 Internet
Standards is discontinued.
The Regional Internet Registries (RIRs) are advised that maintenance
of delegation of entries in "ip6.int" is no longer required as part
of infrastructure services in support of Internet Standards
Conformant IPv6 implementations as of 1 September 2005. The RIRs are
requested to work with their communities to adopt a schedule
regarding the cessation of support of registration services for the
"ip6.int" domain.
2. IANA Considerations
IANA is advised that the "ip6.int" domain for reverse mapping of IPv6
addresses to domain names is no longer part of Internet Standards
Conformant support of IPv6 as of 1 September 2005.
3. Security Considerations
While DNS spoofing of address to name mapping has been exploited in
IPv4, removal of the "ip6.int" zone from the standard IPv6
specification creates no new threats to the security of the internet.
4. Acknowledgements
The document was prepared with the assistance of Kurt Lindqvist,
Thomas Narten, Paul Wilson, David Kessens, Bob Hinden, Brian
Haberman, and Bill Manning.
5. Normative References
[RFC3152] Bush, R., "Delegation of IP6.ARPA", BCP 49, RFC 3152,
August 2001.
[RFC3596] Thomson, S., Huitema, C., Ksinant, V., and M. Souissi, "DNS
Extensions to Support IP Version 6", RFC 3596, October
2003.
Author's Address
Geoff Huston
APNIC
EMail: gih@apnic.net
Full Copyright Statement
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AI ELI5
On this page
§1The IPv6 Standards Change
When IPv6 addresses first needed to be mapped back to domain names through the Domain Name System, the IETF initially used the ip6.int domain for this purpose. In August 2001, RFC 3152 recommended deprecating ip6.int in favor of ip6.arpa, following the pattern already established for IPv4 reverse lookups, which use in-addr.arpa.
This RFC formally completes that transition. As of September 1, 2005, standards-conformant IPv6 implementations must use ip6.arpa and are no longer permitted to use ip6.int for reverse DNS lookups.
When computers look up what website an address belongs to, they used to ask about a place called ip6.int. Now they should ask about ip6.arpa instead, which is better organized.
§2New Domain Requirements
Reverse DNS for IPv6 addresses works by taking the address and converting it into a DNS query. For example, an IPv6 address is written in reverse order, hex digit by hex digit, and appended to the domain name. Under the old standard, this query was made against ip6.int. The new standard directs all such queries to ip6.arpa instead.
The Regional Internet Registries (RIRs), which manage IP address assignments, were directed to stop maintaining the ip6.int zone and transition their infrastructure to support ip6.arpa for IPv6 reverse lookups.
Instead of asking a directory called ip6.int for an address lookup, you now ask ip6.arpa. It is the same kind of question, just sent to a different directory.
§3Security and Compatibility
The change from ip6.int to ip6.arpa creates no new security threats. While DNS spoofing of address-to-name mappings has been exploited in IPv4, the removal of ip6.int from the standard specification simply closes one old path and directs users to the newer, standardized one.
This alignment with IPv4's approach (which already used the .arpa domain) makes IPv6 reverse DNS more consistent with existing Internet infrastructure and standards practices.
Switching to a new directory does not make things less safe. Everyone now looks in one place (ip6.arpa) instead of some old place (ip6.int), making things simpler and more organized.