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rfc:rfc3330

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.

IANA Informational [Page 1] RFC 3330 Special-Use IPv4 Addresses September 2002

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.

IANA Informational [Page 2] RFC 3330 Special-Use IPv4 Addresses September 2002

 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.

IANA Informational [Page 3] RFC 3330 Special-Use IPv4 Addresses September 2002

 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

IANA Informational [Page 4] RFC 3330 Special-Use IPv4 Addresses September 2002

 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.

IANA Informational [Page 5] RFC 3330 Special-Use IPv4 Addresses September 2002

 [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

IANA Informational [Page 6] RFC 3330 Special-Use IPv4 Addresses September 2002

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.

IANA Informational [Page 7]

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