IANA Guidelines for IPv4 Multicast Address Assignments
RFC 3171

Document Type RFC - Best Current Practice (August 2001; Errata)
Obsoleted by RFC 5771
Authors IANA  , Kevin Almeroth  , Zaid AlBanna  , David Meyer 
Last updated 2020-01-21
Stream IETF
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IESG IESG state RFC 3171 (Best Current Practice)
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Network Working Group                                         Z. Albanna
Request for Comments: 3171                              Juniper Networks
BCP: 51                                                      K. Almeroth
Category: Best Current Practice                                     UCSB
                                                                D. Meyer
                                                             M. Schipper
                                                             August 2001

         IANA Guidelines for IPv4 Multicast Address Assignments

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 (2001).  All Rights Reserved.


   This memo provides guidance for the Internet Assigned Numbers
   Authority (IANA) in assigning IPv4 multicast addresses.

1. Introduction

   The Internet Assigned Numbers Authority (IANA) (www.iana.org) is
   charged with allocating parameter values for fields in protocols
   which have been designed, created or are maintained by the Internet
   Engineering Task Force (IETF).  RFC 2780 [RFC2780] provides the IANA
   guidance in the assignment of parameters for fields in newly
   developed protocols.  This memo expands on section 4.4.2 of RFC 2780
   and attempts to codify existing IANA practice used in the assignment
   IPv4 multicast addresses.

   The terms "Specification Required", "Expert Review", "IESG Approval",
   "IETF Consensus", and "Standards Action", are used in this memo to
   refer to the processes described in [RFC2434].  The keywords MUST,
   SHOULD, SHOULD NOT are to be interpreted as defined in RFC 2119

Albanna, et al.          Best Current Practice                  [Page 1]
RFC 3171             IANA IPv4 Multicast Guidelines          August 2001

   In general, due to the relatively small size of the IPv4 multicast
   addresses space, further assignment of IPv4 multicast address space
   is recommended only in limited circumstances.  Specifically, the IANA
   should only assign addresses in those cases where the dynamic
   selection (SDP/SAP), GLOP, SSM or Administratively Scoped address
   spaces cannot be used.  The guidelines described below are reflected
   in http://www.iana.org/numbers.html.

2. Definition of Current Assignment Practice

   Unlike IPv4 unicast address assignment, where blocks of addresses are
   delegated to regional registries, IPv4 multicast addresses are
   assigned directly by the IANA.  Current assignments appear as follows
   [IANA]:   -     (224.0.0/24)  Local Network Control Block   -     (224.0.1/24)  Internetwork Control Block   -                   AD-HOC Block   -   (224.1/16)    ST Multicast Groups   -   (224.2/16)    SDP/SAP Block -               DIS Transient Block   -               RESERVED   - (232/8)       Source Specific Multicast
                                               Block   - (233/8)       GLOP Block   -               RESERVED   - (239/8)       Administratively Scoped

   The IANA generally assigns addresses from the Local Network Control,
   Internetwork Control, and AD-HOC blocks.  Assignment guidelines for
   each of these blocks, as well as for the Source Specific Multicast,
   GLOP and Administratively Scoped Blocks, are described below.

3. Local Network Control Block (224.0.0/24)

   Addresses in the Local Network Control block are used for protocol
   control traffic that is not forwarded off link.  Examples of this
   type of use include OSPFIGP All Routers ( [RFC2328].

3.1. Assignment Guidelines

   Pursuant to section 4.4.2 of RFC 2780 [RFC2780], assignments from the
   Local Network Control block follow an Expert Review, IESG Approval or
   Standards Action process.  See [IANA] for the current set of

Albanna, et al.          Best Current Practice                  [Page 2]
RFC 3171             IANA IPv4 Multicast Guidelines          August 2001

4. Internetwork Control Block (224.0.1/24)

   Addresses in the Internetwork Control block are used for protocol
   control that must be forwarded through the Internet.  Examples
   include (NTP [RFC2030]) and (mdhcpdiscover

4.1. Assignment Guidelines
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