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rfc:rfc5735

Internet Engineering Task Force (IETF) M. Cotton Request for Comments: 5735 L. Vegoda BCP: 153 ICANN Obsoletes: 3330 January 2010 Category: Best Current Practice ISSN: 2070-1721

                     Special Use IPv4 Addresses

Abstract

 This document obsoletes RFC 3330.  It 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, nor does it address IPv4 address space assigned
 directly by IANA prior to the creation of the Regional Internet
 Registries.  It also does not address allocations or assignments of
 IPv6 addresses or autonomous system numbers.

Status of This Memo

 This memo documents an Internet Best Current Practice.
 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).  Further information on
 BCPs is available in 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/rfc5735.

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

Cotton & Vegoda Best Current Practice [Page 1] RFC 5735 Special Use IPv4 Addresses January 2010

 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.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Global and Other Specialized Address Blocks . . . . . . . . . 3 4. Summary Table . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Assignments of IPv4 Blocks for New Specialized Uses . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7

9.1.  Normative References . . . . . . . . . . . . . . . . . . .  7
9.2.  Informative References . . . . . . . . . . . . . . . . . .  7

Appendix A. Differences between This Document and RFC 3330 . . . 10

Cotton & Vegoda Best Current Practice [Page 2] RFC 5735 Special Use IPv4 Addresses January 2010

1. Introduction

 Throughout its 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
 (RIRs) according to their established needs.  These RIRs are
 responsible for the registration of IPv4 addresses to operators and
 users of the Internet within their regions.
 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 that document describes that assignment process.
 Small 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 and provide a current list of
 special use IPv4 addresses.
 This document is a revision of RFC 3330 [RFC3330], which it
 obsoletes; its primary purpose is to reflect the changes to the list
 of special IPv4 assignments since the publication of RFC 3330.  It is
 a companion to [RFC5156], which describes special IPv6 addresses.

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. 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 ([RFC1122], Section
 3.2.1.3).
 10.0.0.0/8 - This block is set aside for use in private networks.
 Its intended use is documented in [RFC1918].  As described in that
 RFC, addresses within this block do not legitimately appear on the
 public Internet.  These addresses can be used without any
 coordination with IANA or an Internet registry.

Cotton & Vegoda Best Current Practice [Page 3] RFC 5735 Special Use IPv4 Addresses January 2010

 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 loops back inside the host.  This
 is ordinarily implemented using only 127.0.0.1/32 for loopback.  As
 described in [RFC1122], Section 3.2.1.3, addresses within the entire
 127.0.0.0/8 block do not legitimately appear on any network anywhere.
 169.254.0.0/16 - This is the "link local" block.  As described in
 [RFC3927], it is allocated for communication between hosts on a
 single link.  Hosts obtain these addresses by auto-configuration,
 such as when a DHCP server cannot be found.
 172.16.0.0/12 - This block is set aside for use in private networks.
 Its intended use is documented in [RFC1918].  As described in that
 RFC, addresses within this block do not legitimately appear on the
 public Internet.  These addresses can be used without any
 coordination with IANA or an Internet registry.
 192.0.0.0/24 - This block is reserved for IETF protocol assignments.
 At the time of writing this document, there are no current
 assignments.  Allocation policy for future assignments is given in
 [RFC5736].
 192.0.2.0/24 - This block is assigned as "TEST-NET-1" 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.  As described in [RFC5737], addresses within this
 block do not legitimately appear on the public Internet and can be
 used without any coordination with IANA or an Internet registry.  See
 [RFC1166].
 192.88.99.0/24 - This block is allocated for use as 6to4 relay
 anycast addresses, in [RFC3068].  In contrast with previously
 described blocks, packets destined to addresses from this block do
 appear in the public Internet.  [RFC3068], Section 7, describes
 operational practices to prevent the malicious use of this block in
 routing protocols.
 192.168.0.0/16 - This block is set aside for use in private networks.
 Its intended use is documented in [RFC1918].  As described in that
 RFC, addresses within this block do not legitimately appear on the
 public Internet.  These addresses can be used without any
 coordination with IANA or an Internet registry.
 198.18.0.0/15 - This block has been allocated for use in benchmark
 tests of network interconnect devices.  [RFC2544] explains that this
 range was assigned to minimize the chance of conflict in case a

Cotton & Vegoda Best Current Practice [Page 4] RFC 5735 Special Use IPv4 Addresses January 2010

 testing device were to be accidentally connected to part of the
 Internet.  Packets with source addresses from this range are not
 meant to be forwarded across the Internet.
 198.51.100.0/24 - This block is assigned as "TEST-NET-2" 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.  As described in [RFC5737], addresses within this
 block do not legitimately appear on the public Internet and can be
 used without any coordination with IANA or an Internet registry.
 203.0.113.0/24 - This block is assigned as "TEST-NET-3" 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.  As described in [RFC5737], addresses within this
 block do not legitimately appear on the public Internet and can be
 used without any coordination with IANA or an Internet registry.
 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 for future use; see [RFC1112], Section 4.
 The one exception to this is the "limited broadcast" destination
 address 255.255.255.255.  As described in [RFC0919] and [RFC0922],
 packets with this destination address are not forwarded at the IP
 layer.

Cotton & Vegoda Best Current Practice [Page 5] RFC 5735 Special Use IPv4 Addresses January 2010

4. Summary Table

Address Block Present Use Reference


0.0.0.0/8 "This" Network RFC 1122, Section 3.2.1.3 10.0.0.0/8 Private-Use Networks RFC 1918 127.0.0.0/8 Loopback RFC 1122, Section 3.2.1.3 169.254.0.0/16 Link Local RFC 3927 172.16.0.0/12 Private-Use Networks RFC 1918 192.0.0.0/24 IETF Protocol Assignments RFC 5736 192.0.2.0/24 TEST-NET-1 RFC 5737 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

198.51.100.0/24 TEST-NET-2 RFC 5737 203.0.113.0/24 TEST-NET-3 RFC 5737 224.0.0.0/4 Multicast RFC 3171 240.0.0.0/4 Reserved for Future Use RFC 1112, Section 4 255.255.255.255/32 Limited Broadcast RFC 919, Section 7

                                             RFC 922, Section 7

5. 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 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 [RFC5226].  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.

Cotton & Vegoda Best Current Practice [Page 6] RFC 5735 Special Use IPv4 Addresses January 2010

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. 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
 a private address space such as the 10.0.0.0/8 block or the link
 local block 169.254.0.0/16 originate within your subnet, all routers
 at the border of your network should filter such packets that
 originate from outside your network.  Attacks have been mounted that
 depend on the unexpected use of some of these addresses.
 It should also be noted that some of these address spaces may be used
 legitimately outside a single administrative domain, and may appear
 on the global Internet.  Security policy SHOULD NOT blindly filter
 all of these address spaces without due consideration, and network
 operators are encouraged to review this document, and references
 contained therein, and determine what security policies should be
 associated with each of these address blocks within their specific
 operating environments.

8. Acknowledgments

 Many people have made comments on draft versions of this document.
 The authors would especially like to thank Scott Bradner, Randy Bush,
 Harald Alvestrand, Peter Koch, Alfred Hoenes, and Jari Arkko for
 their constructive feedback and comments.  They would also like to
 offer a special note of thanks to APNIC, which nominated
 198.51.100.0/24 and 203.0.113.0/24.

9. References

9.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.

9.2. Informative References

 [RFC0919]  Mogul, J., "Broadcasting Internet Datagrams", STD 5,
            RFC 919, October 1984.

Cotton & Vegoda Best Current Practice [Page 7] RFC 5735 Special Use IPv4 Addresses January 2010

 [RFC0922]  Mogul, J., "Broadcasting Internet datagrams in the
            presence of subnets", STD 5, RFC 922, October 1984.
 [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
            RFC 1112, August 1989.
 [RFC1122]  Braden, R., "Requirements for Internet Hosts -
            Communication Layers", STD 3, RFC 1122, October 1989.
 [RFC1166]  Kirkpatrick, S., Stahl, M., and M. Recker, "Internet
            numbers", RFC 1166, July 1990.
 [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", RFC 1700,
            October 1994.
 [RFC1918]  Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
            E. Lear, "Address Allocation for Private Internets",
            BCP 5, RFC 1918, February 1996.
 [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.
 [RFC3330]  IANA, "Special-Use IPv4 Addresses", RFC 3330,
            September 2002.
 [RFC3927]  Cheshire, S., Aboba, B., and E. Guttman, "Dynamic
            Configuration of IPv4 Link-Local Addresses", RFC 3927,
            May 2005.
 [RFC5156]  Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156,
            April 2008.

Cotton & Vegoda Best Current Practice [Page 8] RFC 5735 Special Use IPv4 Addresses January 2010

 [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
            IANA Considerations Section in RFCs", BCP 26, RFC 5226,
            May 2008.
 [RFC5736]  Huston, G., Cotton, M., and L. Vegoda, "IANA IPv4 Special
            Purpose Address Registry", RFC 5736, January 2010.
 [RFC5737]  Arkko, J., Cotton, M., and L. Vegoda, "IPv4 Address Blocks
            Reserved for Documentation", RFC 5737, January 2010.

Cotton & Vegoda Best Current Practice [Page 9] RFC 5735 Special Use IPv4 Addresses January 2010

Appendix A. Differences between This Document and RFC 3330

 Address blocks that were reserved for a special purpose in RFC 3330
 but are no longer reserved for any special purpose and are available
 for allocation are no longer listed in Sections 4 or 5.  The
 following blocks have become available:
  1. 14.0.0.0/8 is no longer set aside for assignments to the

international system of Public Data Networks [RFC1700], page 181.

    It is now available for allocation to RIRs in the normal way.
  1. 24.0.0.0/8 is no longer listed as the addresses in that block have

been managed by the American Registry for Internet Numbers (ARIN)

    in the normal way since 2001.
  1. 39.0.0.0/8 is no longer listed as it has been subject to

allocation to an RIR for assignment in the normal manner since

    2001.
  1. 128.0.0.0/16 is not reserved and is subject to future allocation

by a Regional Internet Registry for assignment in the normal

    manner.
  1. 191.255.0.0/16 is not reserved and is subject to future allocation

by a RIR for assignment in the normal manner.

  1. 198.51.100.0/24 is assigned as "TEST-NET-2" for use in

documentation and example code.

  1. 203.0.113.0/24 is assigned as "TEST-NET-3" for use in

documentation and example code.

  1. 223.255.255.0/24 is not reserved and is subject to future

allocation by an RIR for assignment in the normal manner.

Cotton & Vegoda Best Current Practice [Page 10] RFC 5735 Special Use IPv4 Addresses January 2010

Authors' Addresses

 Michelle Cotton
 Internet Corporation for Assigned Names and Numbers
 4676 Admiralty Way, Suite 330
 Marina del Rey, CA  90292
 USA
 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, CA  90292
 USA
 Phone: +1-310-823-9358
 EMail: leo.vegoda@icann.org
 URI:   http://www.iana.org/

Cotton & Vegoda Best Current Practice [Page 11]

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