Network Working Group                                               IANA
Request for Comments: 3330                                September 2002
Category: Informational


                       Special-Use IPv4 Addresses

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This document describes the global and other specialized IPv4 address
   blocks that have been assigned by the Internet Assigned Numbers
   Authority (IANA).  It does not address IPv4 address space assigned to
   operators and users through the Regional Internet Registries.  It
   also does not address allocations or assignments of IPv6 addresses or
   autonomous system numbers.

1. Introduction

   Throughout its entire history, the Internet has employed a central
   Internet Assigned Numbers Authority (IANA) responsible for the
   allocation and assignment of various identifiers needed for the
   operation of the Internet [RFC1174].  In the case of the IPv4 address
   space, the IANA allocates parts of the address space to Regional
   Internet Registries according to their established needs.  These
   Regional Internet Registries are responsible for the assignment of
   IPv4 addresses to operators and users of the Internet within their
   regions.

   Minor portions of the IPv4 address space have been allocated or
   assigned directly by the IANA for global or other specialized
   purposes.  These allocations and assignments have been documented in
   a variety of RFCs and other documents.  This document is intended to
   collect these scattered references.

   On an ongoing basis, the IANA has been designated by the IETF to make
   assignments in support of the Internet Standards Process [RFC2860].
   Section 4 of this document describes that assignment process.




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2. Global and Other Specialized Address Blocks

   0.0.0.0/8 - Addresses in this block refer to source hosts on "this"
   network.  Address 0.0.0.0/32 may be used as a source address for this
   host on this network; other addresses within 0.0.0.0/8 may be used to
   refer to specified hosts on this network [RFC1700, page 4].

   10.0.0.0/8 - This block is set aside for use in private networks.
   Its intended use is documented in [RFC1918].  Addresses within this
   block should not appear on the public Internet.

   14.0.0.0/8 - This block is set aside for assignments to the
   international system of Public Data Networks [RFC1700, page 181]. The
   registry of assignments within this block can be accessed from the
   "Public Data Network Numbers" link on the web page at
   http://www.iana.org/numbers.html.  Addresses within this block are
   assigned to users and should be treated as such.

   24.0.0.0/8 - This block was allocated in early 1996 for use in
   provisioning IP service over cable television systems.  Although the
   IANA initially was involved in making assignments to cable operators,
   this responsibility was transferred to American Registry for Internet
   Numbers (ARIN) in May 2001.  Addresses within this block are assigned
   in the normal manner and should be treated as such.

   39.0.0.0/8 - This block was used in the "Class A Subnet Experiment"
   that commenced in May 1995, as documented in [RFC1797].  The
   experiment has been completed and this block has been returned to the
   pool of addresses reserved for future allocation or assignment.  This
   block therefore no longer has a special use and is subject to
   allocation to a Regional Internet Registry for assignment in the
   normal manner.

   127.0.0.0/8 - This block is assigned for use as the Internet host
   loopback address.  A datagram sent by a higher level protocol to an
   address anywhere within this block should loop back inside the host.
   This is ordinarily implemented using only 127.0.0.1/32 for loopback,
   but no addresses within this block should ever appear on any network
   anywhere [RFC1700, page 5].

   128.0.0.0/16 - This block, corresponding to the numerically lowest of
   the former Class B addresses, was initially and is still reserved by
   the IANA.  Given the present classless nature of the IP address
   space, the basis for the reservation no longer applies and addresses
   in this block are subject to future allocation to a Regional Internet
   Registry for assignment in the normal manner.





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   169.254.0.0/16 - This is the "link local" block.  It is allocated for
   communication between hosts on a single link.  Hosts obtain these
   addresses by auto-configuration, such as when a DHCP server may not
   be found.

   172.16.0.0/12 - This block is set aside for use in private networks.
   Its intended use is documented in [RFC1918].  Addresses within this
   block should not appear on the public Internet.

   191.255.0.0/16 - This block, corresponding to the numerically highest
   to the former Class B addresses, was initially and is still reserved
   by the IANA.  Given the present classless nature of the IP address
   space, the basis for the reservation no longer applies and addresses
   in this block are subject to future allocation to a Regional Internet
   Registry for assignment in the normal manner.

   192.0.0.0/24 - This block, corresponding to the numerically lowest of
   the former Class C addresses, was initially and is still reserved by
   the IANA.  Given the present classless nature of the IP address
   space, the basis for the reservation no longer applies and addresses
   in this block are subject to future allocation to a Regional Internet
   Registry for assignment in the normal manner.

   192.0.2.0/24 - This block is assigned as "TEST-NET" for use in
   documentation and example code.  It is often used in conjunction with
   domain names example.com or example.net in vendor and protocol
   documentation.  Addresses within this block should not appear on the
   public Internet.

   192.88.99.0/24 - This block is allocated for use as 6to4 relay
   anycast addresses, according to [RFC3068].

   192.168.0.0/16 - This block is set aside for use in private networks.
   Its intended use is documented in [RFC1918].  Addresses within this
   block should not appear on the public Internet.

   198.18.0.0/15 - This block has been allocated for use in benchmark
   tests of network interconnect devices.  Its use is documented in
   [RFC2544].

   223.255.255.0/24 - This block, corresponding to the numerically
   highest of the former Class C addresses, was initially and is still
   reserved by the IANA.  Given the present classless nature of the IP
   address space, the basis for the reservation no longer applies and
   addresses in this block are subject to future allocation to a
   Regional Internet Registry for assignment in the normal manner.





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   224.0.0.0/4 - This block, formerly known as the Class D address
   space, is allocated for use in IPv4 multicast address assignments.
   The IANA guidelines for assignments from this space are described in
   [RFC3171].

   240.0.0.0/4 - This block, formerly known as the Class E address
   space, is reserved.  The "limited broadcast" destination address
   255.255.255.255 should never be forwarded outside the (sub-)net of
   the source.  The remainder of this space is reserved for future use.
   [RFC1700, page 4]

3. Summary Table

   Address Block             Present Use                       Reference
   ---------------------------------------------------------------------
   0.0.0.0/8            "This" Network                 [RFC1700, page 4]
   10.0.0.0/8           Private-Use Networks                   [RFC1918]
   14.0.0.0/8           Public-Data Networks         [RFC1700, page 181]
   24.0.0.0/8           Cable Television Networks                    --
   39.0.0.0/8           Reserved but subject
                           to allocation                       [RFC1797]
   127.0.0.0/8          Loopback                       [RFC1700, page 5]
   128.0.0.0/16         Reserved but subject
                           to allocation                             --
   169.254.0.0/16       Link Local                                   --
   172.16.0.0/12        Private-Use Networks                   [RFC1918]
   191.255.0.0/16       Reserved but subject
                           to allocation                             --
   192.0.0.0/24         Reserved but subject
                           to allocation                             --
   192.0.2.0/24         Test-Net
   192.88.99.0/24       6to4 Relay Anycast                     [RFC3068]
   192.168.0.0/16       Private-Use Networks                   [RFC1918]
   198.18.0.0/15        Network Interconnect
                           Device Benchmark Testing            [RFC2544]
   223.255.255.0/24     Reserved but subject
                           to allocation                             --
   224.0.0.0/4          Multicast                              [RFC3171]
   240.0.0.0/4          Reserved for Future Use        [RFC1700, page 4]

4. Assignments of IPv4 Blocks for New Specialized Uses

   The IANA has responsibility for making assignments of protocol
   parameters used in the Internet according to the requirements of the
   "Memorandum of Understanding Concerning the Technical Work of the
   Internet Assigned Numbers Authority" [RFC2860].  Among other things,
   [RFC2860] requires that protocol parameters be assigned according to




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   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.

   The domain name and IP address spaces involve policy issues (in
   addition to technical issues) so that the requirements of [RFC2860]
   do not apply generally to those spaces.  Nonetheless, the IANA is
   responsible for ensuring assignments of IPv4 addresses as needed in
   support of the Internet Standards Process.  When a portion of the
   IPv4 address space is specifically required by an RFC, the technical
   requirements (e.g., size, prefix length) for the portion should be
   described [RFC2434].  Immediately before the RFC is published, the
   IANA will, in consultation with the Regional Internet Registries,
   make the necessary assignment and notify the RFC Editor of the
   particulars for inclusion in the RFC as published.

   As required by [RFC2860], the IANA will also make necessary
   experimental assignments of IPv4 addresses, also in consultation with
   the Regional Internet Registries.

5. Security Considerations

   The particular assigned values of special-use IPv4 addresses
   cataloged in this document do not directly raise security issues.
   However, the Internet does not inherently protect against abuse of
   these addresses; if you expect (for instance) that all packets from
   the 10.0.0.0/8 block originate within your subnet, all border routers
   should filter such packets that originate from elsewhere.  Attacks
   have been mounted that depend on the unexpected use of some of these
   addresses.

6. IANA Considerations

   This document describes the IANA's past and current practices and
   does not create any new requirements for assignments or allocations
   by the IANA.

7. References

   [RFC1174] Cerf, V., "IAB Recommended Policy on Distributing Internet
             Identifier Assignment and IAB Recommended Policy Change to
             Internet 'Connected' Status", RFC 1174, August 1990.

   [RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC
             1700, October 1994.

   [RFC1797] IANA, "Class A Subnet Experiment", RFC 1797, April 1995.




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   [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
             J., and E. Lear, "Address Allocation for Private
             Internets", BCP 5, RFC 1918, February 1996.

   [RFC2050] Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and
             J. Postel, "Internet Registry IP Allocation Guidelines",
             BCP 12, RFC 2050, November 1996.

   [RFC2434] Narten, T., and H. Alvestrand, "Guidelines for Writing an
             IANA Considerations Section in RFCs", BCP 26, RFC 2434,
             October 1998.

   [RFC2544] Bradner, S., and J. McQuaid, "Benchmarking Methodology for
             Network Interconnect Devices", RFC 2544, March 1999.

   [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.

   [RFC3068] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
             RFC 3068, June 2001.

   [RFC3171] Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper,
             "IANA Guidelines for IPv4 Multicast Address Assignments",
             BCP 51, RFC 3171, August 2001.

   [RFC3232] Reynolds, J. Ed., "Assigned Numbers: RFC 1700 is Replaced
             by an On-line Database", RFC 3232, January 2002.

8. Acknowledgments

   Many people have made comments on draft versions of this document.
   The IANA would especially like to thank Scott Bradner, Randy Bush,
   and Harald Alvestrand for their constructive feedback and comments.

9. Author's Address

   Internet Assigned Numbers Authority (IANA)
   4676 Admiralty Way, Suite 330
   Marina del Rey, CA 90292-6601

   Phone: +1 310-823-9358
   Fax:   +1 310-823-8649
   EMail: iana@iana.org







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10.  Full Copyright Statement

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph are
   included on all such copies and derivative works.  However, this
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

   Funding for the RFC Editor function is currently provided by the
   Internet Society.



















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