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IETF RFC 3330
Special-Use IPv4 Addresses
Last modified on Tuesday, October 1st, 2002
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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 © 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 [RFC 1174]. 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 [RFC 2860].
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 [RFC 1700, page 4].
10.0.0.0/8 - This block is set aside for use in private networks.
Its intended use is documented in [RFC 1918]. 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 [RFC 1700, 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 [RFC 1797]. 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 [RFC 1700, 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 [RFC 1918]. 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 [RFC 3068].
192.168.0.0/16 - This block is set aside for use in private networks.
Its intended use is documented in [RFC 1918]. 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
[RFC 2544].
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
[RFC 3171].
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.
[RFC 1700, page 4]
3. Summary Table
Address Block Present Use Reference
---------------------------------------------------------------------
0.0.0.0/8 "This" Network [RFC 1700, page 4]
10.0.0.0/8 Private-Use Networks [RFC 1918]
14.0.0.0/8 Public-Data Networks [RFC 1700, page 181]
24.0.0.0/8 Cable Television Networks --
39.0.0.0/8 Reserved but subject
to allocation [RFC 1797]
127.0.0.0/8 Loopback [RFC 1700, 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 [RFC 1918]
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 [RFC 3068]
192.168.0.0/16 Private-Use Networks [RFC 1918]
198.18.0.0/15 Network Interconnect
Device Benchmark Testing [RFC 2544]
223.255.255.0/24 Reserved but subject
to allocation --
224.0.0.0/4 Multicast [RFC 3171]
240.0.0.0/4 Reserved for Future Use [RFC 1700, 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" [RFC 2860]. Among other things,
[RFC 2860] 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 [RFC 2860]
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 [RFC 2434]. 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 [RFC 2860], 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
[RFC 1174] Cerf, V., "IAB Recommended Policy on Distributing Internet
Identifier Assignment and IAB Recommended Policy Change to
Internet 'Connected' Status", RFC 1174, August 1990.
[RFC 1700] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC
1700, October 1994.
[RFC 1797] IANA, "Class A Subnet Experiment", RFC 1797, April 1995.
IANA Informational PAGE 5
RFC 3330 Special-Use IPv4 Addresses September 2002
[RFC 1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
J., and E. Lear, "Address Allocation for Private
Internets", BCP 5, RFC 1918, February 1996.
[RFC 2050] Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and
J. Postel, "Internet Registry IP Allocation Guidelines",
BCP 12, RFC 2050, November 1996.
[RFC 2434] Narten, T., and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC 2544] Bradner, S., and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999.
[RFC 2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
Understanding Concerning the Technical Work of the Internet
Assigned Numbers Authority", RFC 2860, June 2000.
[RFC 3068] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
RFC 3068, June 2001.
[RFC 3171] Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper,
"IANA Guidelines for IPv4 Multicast Address Assignments",
BCP 51, RFC 3171, August 2001.
[RFC 3232] 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 © 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
Special-Use IPv4 Addresses
RFC TOTAL SIZE: 16200 bytes
PUBLICATION DATE: Tuesday, October 1st, 2002
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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