RFC 3171 (rfc3171) - Page 2 of 8

IANA Guidelines for IPv4 Multicast Address Assignments

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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]:

   224.0.0.0   - 224.0.0.255     (224.0.0/24)  Local Network Control Block
   224.0.1.0   - 224.0.1.255     (224.0.1/24)  Internetwork Control Block
   224.0.2.0   - 224.0.255.0                   AD-HOC Block
   224.1.0.0   - 224.1.255.255   (224.1/16)    ST Multicast Groups
   224.2.0.0   - 224.2.255.255   (224.2/16)    SDP/SAP Block
   224.252.0.0 - 224.255.255.255               DIS Transient Block
   225.0.0.0   - 231.255.255.255               RESERVED
   232.0.0.0   - 232.255.255.255 (232/8)       Source Specific Multicast
                                               Block
   233.0.0.0   - 233.255.255.255 (233/8)       GLOP Block
   234.0.0.0   - 238.255.255.255               RESERVED
   239.0.0.0   - 239.255.255.255 (239/8)       Administratively Scoped
                                               Block

   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 (224.0.0.5) [RFC 2328].

3.1. Assignment Guidelines

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





Albanna, et al.          Best Current Practice
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