RFC 2780 (rfc2780) - Page 3 of 10

IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers

RFC 2780                    IANA Assignments                  March 2000


4.4 IPv4 Source and Destination addresses

   The IPv4 source and destination addresses use the same namespace but
   do not necessarily use the same values.  Values in these fields fall
   into a number of ranges defined in [V4] and [MULT].

4.4.1 IPv4 Unicast addresses

   The Internet Corporation for Assigned Names and Numbers (ICANN)
   recently accepted responsibility for the formulation of specific
   guidelines for the allocation of the values from the IPv4 unicast
   address space (values 0.0.0.0 through 223.255.255.255 ) other than
   values from the ranges 0/8 (which was reserved in [AN80]) and 127/8
   (from which the loopback address has been taken) along with other
   values already assigned by the IETF for special functions or
   purposes. (For example, the private addresses defined in RFC 1918.)
   Further assignments in the 0/8 and 127/8 ranges require a Standards
   Action process since current IP implementations may break if this is
   done.

4.4.2 IPv4 Multicast addresses

   IPv4 addresses that fall in the range from 224.0.0.0 through
   239.255.255.255 are known as multicast addresses.  The IETF through
   its normal processes has assigned a number of IPv4 multicast
   addresses for special purposes. For example, [ADSCP] assigned a
   number of IPv4 multicast address to correspond to IPv6 scoped
   multicast addresses.  Also, the values in the range from 224.0.0.0 to
   224.0.0.255 , inclusive, are reserved by the IANA for the use of
   routing protocols and other low-level topology discovery or
   maintenance protocols, such as gateway discovery and group membership
   reporting. (See the IANA web page) New values in this range are
   assigned following an IESG Approval or Standards Action process.
   Assignments of individual multicast address follow an Expert Review,
   IESG Approval or Standards Action process.  Until further work is
   done on multicast protocols, large-scale assignments of IPv4
   multicast addresses is not recommended.

   From time to time, there are requests for temporary assignment of
   multicast space for experimental purposes.  These will originate in
   an IESG Approval process and should be for a limited duration such as
   one year.

4.4.3 IPv4 Reserved addresses

   IPv4 addresses in the range from 240.0.0.0 through 255.255.255.254
   are reserved [AN81, MULT] and compliant IPv4 implementations will
   discard any packets that make use of them.  Addresses in this range



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