RFC 5736

IANA IPv4 Special Purpose Address Registry

📅 published January 2010, from ietf

RFC 5736: IANA IPv4 Special Purpose Address Registry ✨

Hiii bestie, this is RFC 5736 🎀, and it's the one that sets up the IANA IPv4 Special Purpose Address Registry. It was published as an Informational document (not a Standards Track spec) in January 2010, with ISSN 2070-1721. The authors are Geoff Huston (APNIC), Michelle Cotton (ICANN), and Leo Vegoda (ICANN). It doesn't obsolete or update any RFCs, since the header doesn't list any. 💅

Abstract

okay so this one is basically a direction to IANA about creating and managing the IANA IPv4 Special Purpose Address Registry 🦋

Status of This Memo

This doc is not an Internet Standards Track spec. It's just published for informational purposes 🧚

It's a product of the IETF, it reflects the consensus of the IETF community, it got public review, and the IESG approved it for publication. Not every IESG-approved doc is a candidate for any level of Internet Standard, so see Section 2 of RFC 5741 for that. 🌸

If you want the current status, any errata, or a way to send feedback, check http://www.rfc-editor.org/info/rfc5736.

Copyright Notice

This doc is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) as in effect on the date it was published. Please read these carefully, because they spell out your rights and restrictions for this doc. Code Components pulled out of this doc must include Simplified BSD License text, as described in Section 4.e of the Trust Legal Provisions, and they come without warranty, as described in the Simplified BSD License. 💖

1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.  IANA IPv4 Special Purpose Address Block . . . . . . . . . . . . 2
3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
4.  Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 4
6.  Informative References  . . . . . . . . . . . . . . . . . . . . 5

1. Introduction

Okay, so this is a direction to [IANA] about creating and managing the IANA IPv4 Special Purpose Address Registry 🌈 The registry is for recording IETF protocol assignments out of 192.0.0.0/24, plus any other address prefixes that get allocated to the registry later on. Section 3 has the details. ✨

2. IANA IPv4 Special Purpose Address Block

[RFC5735] records the assignment of an IPv4 address prefix to IANA for IETF protocol assignments. 🎀

   192.0.0.0/24 - This block is reserved for IETF protocol
   assignments.

This address allocation to IANA is meant to support IETF protocol assignments. For the bigger picture on IANA's roles in address allocation functions, check out [RFC2860] 💅

   4.3. [...]  Note that [...] (b) assignments of specialised address
   blocks (such as multicast or anycast blocks), and (c) experimental
   assignments are not considered to be policy issues, and shall
   remain subject to the provisions of this Section 4.  (For purposes
   of this MOU, the term "assignments" includes allocations.)

The reference to Section 4 here points to the general technical work IANA does, as described in [RFC2860]:

   4.1.  The IANA will assign and register Internet protocol
   parameters only as directed by the criteria and procedures
   specified in RFCs, including Proposed, Draft, and full Internet
   Standards and Best Current Practice documents, and any other RFC
   that calls for IANA assignment.

This doc directs IANA to designate special purpose address blocks in compliance with [RFC2860]. 🦋

It also directs IANA to open an IPv4 Special Purpose Address Registry for managing those IANA-designated address blocks. Registrations can cover addresses for IETF protocol assignments and other special purpose cases, as long as they're documented in IESG-reviewed RFCs, following the provisions in Section 4.1 of [RFC2860]. It's giving organized 🧚

3. IANA Considerations

IANA maintains an "IANA IPv4 Special Purpose Address Registry". It records the current IANA address designations from the IANA-managed IPv4 Special Purpose address pool. 🍓

This recommendation is about managing the address pool used for IETF protocol assignments, as documented in [RFC5735], which is 192.0.0.0/24. Following the policies outlined in [RFC5226], any further assignments of address space to IANA for later designation of address prefixes for the purposes listed here shall only happen through an IETF Review action. 🔥

IANA may make Special Purpose address designations to support testing or experimental usage activities that the IETF starts, or for specialised use of a designated address block in a context (for example, anycast) associated with an Internet Standards Track protocol. Every one of those address designations must be documented in the "IANA Considerations" section of an IESG-reviewed RFC. 💜

The IANA IPv4 Special Purpose Address Registry records the following for every current address designation IANA has made:

The designated address prefix.
The RFC that called for the IANA address designation.
The date the designation was made.
The date the use designation is to be terminated (if specified as a limited-use designation).
The nature of the purpose of the designated address (for example, unicast experiment or protocol service anycast).
For experimental unicast applications, and otherwise as appropriate, the registry will also identify the entity and related contact details to whom the address designation has been made.
The registry will also note, for each designation, the intended routing scope of the address. That means whether the address is intended to be routable only in scoped, local, or private contexts, or whether the address prefix is intended to be routed globally. 🌸
The date in the IANA registry is the date of the IANA action, meaning the day IANA records the allocation. 🎀

As a general comment, the registry notes that address prefixes listed in the IPv4 Special Purpose Address Registry are not guaranteed routability in any particular local or global context. Lowkey important 🙈

IANA will not maintain any further sub-registries for any IPv4 Special Purpose address block designated under this direction. ✨

4. Security Considerations

Security of the Internet's routing system depends on being able to authenticate an assertion of unique control of an address block. 😭 Measures to authenticate those assertions rely on validating that the address block is part of an existing allocated address block, and that there's a trustable and unique reference in the IANA address registries.

This registry is meant to be an authoritative source of information about the currency and intended purpose of IPv4 Special Purpose address blocks designated from the IANA-administered IPv4 Special Purpose address pool. It's a small step toward a comprehensive registry framework that can serve as a trust point for starting a chain of address validation. 🫶 Consideration should be given to using file signatures and associated certificate mechanisms, so applications can confirm that the registry contents are current and that IANA published them. This part is seriously important, bestie 💀

5. Acknowledgements

This doc is based on [RFC4773], which was prepared with help from Leslie Daigle, Brian Haberman, Bob Hinden, David Kessens, Kurt Lindqvist, Thomas Narten, and Paul Wilson. 👑 Not all of these people were explicitly consulted for this doc, but their original contributions are acknowledged here. Iconic of them 🌈

6. Informative References

[IANA]     IANA, "IANA Matrix for Protocol Parameter Assignment/
           Registration Procedures",
           <http://www.iana.org/numbers.html>.

[RFC2860]  Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
           Understanding Concerning the Technical Work of the
           Internet Assigned Numbers Authority", RFC 2860, June 2000.

[RFC4773]  Huston, G., "Administration of the IANA Special Purpose
           IPv6 Address Block", RFC 4773, December 2006.

[RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
           IANA Considerations Section in RFCs", BCP 26, RFC 5226,
           May 2008.

[RFC5735]  Cotton, M. and L. Vegoda, "Special Use IPv4 Addresses",
           BCP 153, RFC 5735, January 2010.

Authors' Addresses

Geoff Huston 🧚

Asia Pacific Network Information Centre
PO Box 2131
Milton, QLD 4064
Australia
Phone: +61-7-3858-3100
EMail: gih@apnic.net
URI: http://www.apnic.net/

Michelle Cotton 🦋

Internet Corporation for Assigned Names and Numbers
4676 Admiralty Way, Suite 330
Marina del Rey, CA 90292-6601
USA
Phone: +1-310-823-9358
EMail: michelle.cotton@icann.org
URI: http://www.iana.org/

Leo Vegoda 💜

Internet Corporation for Assigned Names and Numbers
4676 Admiralty Way, Suite 330
Marina del Rey, CA 90292-6601
USA
Phone: +1-310-823-9358
EMail: leo.vegoda@icann.org
URI: http://www.iana.org/

📦 where this page comes from

ietf: rfc5736 2010-01
💖 girlified by claude-haiku-5-5 on 2026-10-17: a language model's rewrite of the original, under its terms