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.
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.
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.
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
the criteria and procedures specified in RFCs, including Proposed,
Draft, and full Internet Standards and Best Current Practice
documents, and any other RFCthat 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 RFCis published, the
IANA will, in consultation with the Regional Internet Registries,
make the necessary assignment and notify the RFCEditor of the
particulars for inclusion in the RFCas 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", RFC1174, August 1990.
[RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC
1700, October 1994.
[RFC1797] IANA, "Class A Subnet Experiment", RFC1797, April 1995.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.
J., and E. Lear, "Address Allocation for Private
Internets", BCP 5, RFC1918, February 1996.
[RFC2050] Hubbard, K., Kosters, M., Conrad, D., Karrenberg, D., and
J. Postel, "Internet Registry IP Allocation Guidelines",
BCP 12, RFC2050, November 1996.
[RFC2434] Narten, T., and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC2434,
October 1998.
[RFC2544] Bradner, S., and J. McQuaid, "Benchmarking Methodology for
Network Interconnect Devices", RFC2544, March 1999.
[RFC2860] Carpenter, B., Baker, F., and M. Roberts, "Memorandum of
Understanding Concerning the Technical Work of the Internet
Assigned Numbers Authority", RFC2860, June 2000.
[RFC3068] Huitema, C., "An Anycast Prefix for 6to4 Relay Routers",
RFC3068, June 2001.
[RFC3171] Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper,
"IANA Guidelines for IPv4 Multicast Address Assignments",
BCP 51, RFC3171, August 2001.
[RFC3232] Reynolds, J. Ed., "Assigned Numbers: RFC1700 is Replaced
by an On-line Database", RFC3232, 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
10. Full Copyright Statement
Copyright (C) The Internet Society (2002). All Rights Reserved.
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Acknowledgement
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