IPv4 Documentation: IPv4 Address Blocks Reserved for Documentation
Three IPv4 address blocks set aside so examples in documents never collide with real networks.
Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks Reserved for Documentation", RFC 5737, DOI 10.17487/RFC5737, January 2010, <https://www.rfc-editor.org/info/rfc5737>.
@misc{rfc5737,
series = {Request for Comments},
number = 5737,
howpublished = {RFC 5737},
publisher = {RFC Editor},
doi = {10.17487/RFC5737},
url = {https://www.rfc-editor.org/info/rfc5737},
author = {J. Arkko and M. Cotton and L. Vegoda},
title = {{IPv4 Address Blocks Reserved for Documentation}},
pagetotal = 4,
year = 2010,
month = jan,
} RFC text
Contents
Internet Engineering Task Force (IETF) J. Arkko
Request for Comments: 5737 Ericsson
Updates: 1166 M. Cotton
Category: Informational L. Vegoda
ISSN: 2070-1721 ICANN
January 2010
IPv4 Address Blocks Reserved for Documentation
Abstract
Three IPv4 unicast address blocks are reserved for use in examples in
specifications and other documents. This document describes the use
of these blocks.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5737.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
1. Introduction
This document describes three IPv4 address blocks that are provided
for use in documentation. The use of designated address ranges for
documentation and examples reduces the likelihood of conflicts and
confusion arising from the use of addresses assigned for some other
purpose.
[RFC1166] reserves the first of the three address blocks,
192.0.2.0/24. The other two address blocks have recently been
allocated for this purpose, primarily to ease the writing of examples
involving addresses from multiple networks.
Other documentation ranges have been defined in the IETF, including
the IPv6 documentation prefix [RFC3849] and example domain names
[RFC2606]. Documentation also makes use of the ranges reserved in
[RFC1918].
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, [RFC2119].
3. Documentation Address Blocks
The blocks 192.0.2.0/24 (TEST-NET-1), 198.51.100.0/24 (TEST-NET-2),
and 203.0.113.0/24 (TEST-NET-3) are provided for use in
documentation.
4. Operational Implications
Addresses within the TEST-NET-1, TEST-NET-2, and TEST-NET-3 blocks
SHOULD NOT appear on the public Internet and are used without any
coordination with IANA or an Internet registry [RFC2050]. Network
operators SHOULD add these address blocks to the list of non-
routeable address spaces, and if packet filters are deployed, then
this address block SHOULD be added to packet filters.
These blocks are not for local use, and the filters may be used in
both local and public contexts.
5. The Status of 128.66.0.0/16
Note that 128.66.0.0/16 has been used for some examples in the past.
However, this block did not appear in the list of special prefixes in
[RFC3330] or its successors, and the block is therefore not reserved
for any special purpose. The block can be used for regular address
assignments with caution.
6. Security Considerations
This document has no security implications.
7. IANA Considerations
IANA has recorded the allocation of the three address blocks in the
IPv4 address registry. No end party is to be assigned these
addresses.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[RFC1166] Kirkpatrick, S., Stahl, M., and M. Recker, "Internet
numbers", RFC 1166, July 1990.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., 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.
[RFC2606] Eastlake, D. and A. Panitz, "Reserved Top Level DNS
Names", BCP 32, RFC 2606, June 1999.
[RFC3330] IANA, "Special-Use IPv4 Addresses", RFC 3330,
September 2002.
[RFC3849] Huston, G., Lord, A., and P. Smith, "IPv6 Address Prefix
Reserved for Documentation", RFC 3849, July 2004.
Appendix A. Acknowledgments
The authors would like to offer a special note of thanks to APNIC,
which nominated 198.51.100.0/24 and 203.0.113.0/24 for this purpose.
The authors would also like to acknowledge that this document
inherits material from [RFC3849].
The authors would also like to thank Geoff Huston, Peter Koch, Ulf
Olsson, John Klensin, and others for interesting discussions of this
topic.
Authors' Addresses
Jari Arkko
Ericsson
Jorvas 02420
Finland
EMail: jari.arkko@piuha.net
Michelle Cotton
Internet Corporation for Assigned Names and Numbers
4676 Admiralty Way, Suite 330
Marina del Rey 90292
United States of America
Phone: +1-310-823-9358
EMail: michelle.cotton@icann.org
URI: http://www.iana.org/
Leo Vegoda
Internet Corporation for Assigned Names and Numbers
4676 Admiralty Way, Suite 330
Marina del Rey 90292
United States of America
Phone: +1-310-823-9358
EMail: leo.vegoda@icann.org
URI: http://www.iana.org/
AI ELI5
On this page
§1Why Reserve Example Addresses
Using designated ranges for documentation and examples reduces the chance of conflicts and confusion from using addresses assigned for something else. RFC 1166 had already reserved the first block, 192.0.2.0/24. The other two were recently allocated, mainly to make it easier to write examples that involve addresses from several networks.
Other documentation ranges already exist: the IPv6 documentation prefix (RFC 3849) and example domain names (RFC 2606). Documentation also uses the ranges reserved in RFC 1918.
Textbook writers need pretend addresses, like using "Anytown" instead of a real town. These blocks are the pretend towns.
§2The Three Blocks
The RFC names three blocks, all /24 prefixes: 192.0.2.0/24 (TEST-NET-1), 198.51.100.0/24 (TEST-NET-2) and 203.0.113.0/24 (TEST-NET-3). IANA has recorded the allocation of all three in the IPv4 address registry, and no end party is to be assigned these addresses. The authors thank APNIC, which nominated the second and third blocks.
There are three pretend neighborhoods, and nobody is allowed to really live in them.
- 192.0.2.0/24TEST-NET-1 — First block, already reserved by RFC 1166.
- 198.51.100.0/24TEST-NET-2 — Newly allocated for documentation.
- 203.0.113.0/24TEST-NET-3 — Newly allocated for documentation.
§3Operational Rules and 128.66.0.0/16
Addresses in the TEST-NET blocks SHOULD NOT appear on the public Internet, and they are used without coordination with IANA or an Internet registry. Network operators SHOULD add the blocks to their list of non-routable address space and to packet filters if they are deployed. The blocks are not for local use, and the filters may be used in both local and public contexts.
The RFC also notes that 128.66.0.0/16 has been used in past examples. It was not in the list of special prefixes in RFC 3330 or its successors, so it is not reserved and can be used for regular address assignments with caution. The RFC says it has no security implications.
Real networks should not carry mail to these pretend addresses, so routers are told to block them. The old pretend range 128.66.0.0/16 is not protected and may belong to a real person.