Special Use IPv4 Addresses
draft-iana-rfc3330bis-02

Status of this Memo

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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. It also does not address allocations or assignments of IPv6 addresses or autonomous system numbers. Special IPv6 addresses are described in a companion document that will be published as RFC5156.

Table of Contents

1.  Introduction
2.  Terminology
3.  Differences between this document and RFC 3330
4.  Global and Other Specialized Address Blocks
5.  Summary Table
6.  Assignments of IPv4 Blocks for New Specialized Uses
7.  IANA Considerations
8.  Security Considerations
9.  Acknowledgments
10.  References
    10.1.  Normative References
    10.2.  Informative References
§  Author's Address
§  Intellectual Property and Copyright Statements

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] (Cerf, V., “IAB recommended policy on distributing internet identifier assignment and IAB recommended policy change to internet "connected" status,” August 1990.). 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 Regional Internet Registries are responsible for the assignment of IPv4 addresses to operators and users of the Internet within their regions.

This document is a revision of RFC 3330 [RFC3330] (IANA, “Special-Use IPv4 Addresses,” September 2002.), which it obsoletes; its primary purpose is to re-publish the technical content of RFC 3330 mostly unchanged as a Best Current Practice RFC.

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 and provide a current list of special use IPv4 addresses.

On an ongoing basis, the IANA has been designated by the IETF to make assignments in support of the Internet Standards Process [RFC2860] (Carpenter, B., Baker, F., and M. Roberts, “Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority,” June 2000.). Section 5 of this document describes that assignment process.

The terms "Specification Required", "Expert Review", "IESG Approval", "IETF Consensus", and "Standards Action", are used in this memo to refer to the processes described in [RFC5226] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” May 2008.). The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined in [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

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] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

3.  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 changes: 14.0.0.0/8 is no longer set aside for assignments to the international system of Public Data Networks [RFC1700] (Reynolds, J. and J. Postel, “Assigned Numbers,” October 1994.), page 181]. It is now available for allocation to RIRs in the normal way. 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. 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. 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. 191.255.0.0/16 is not reserved and is subject to future allocation by a RIR for assignment in the normal manner. 192.0.0.0/24 is not reserved and is subject to future allocation by a RIR for assignment in the normal manner. 223.255.255.0/24 is not reserved and is subject to future allocation by an RIR for assignment in the normal manner.

4.  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] (Reynolds, J. and J. Postel, “Assigned Numbers,” October 1994.), page 4.

10.0.0.0/8 - This block is set aside for use in private networks. Its intended use is documented in [RFC1918] (Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, “Address Allocation for Private Internets,” February 1996.). Addresses within this block should not appear on the public Internet.

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] (Reynolds, J. and J. Postel, “Assigned Numbers,” October 1994.), page 5.

128.0.0.0/16 - This block, corresponding to the numerically lowest of the former Class B addresses, was initially 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 by a Regional Internet Registry for assignment in the normal manner.

169.254.0.0/16 - This is the "link local" block. As described in [RFC3927] (Cheshire, S., Aboba, B., and E. Guttman, “Dynamic Configuration of IPv4 Link-Local Addresses,” May 2005.), 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] (Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, “Address Allocation for Private Internets,” February 1996.). Addresses within this block should not appear on the public Internet.

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] (Huitema, C., “An Anycast Prefix for 6to4 Relay Routers,” June 2001.).

192.168.0.0/16 - This block is set aside for use in private networks. Its intended use is documented in [RFC1918] (Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and E. Lear, “Address Allocation for Private Internets,” February 1996.). 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] (Bradner, S. and J. McQuaid, “Benchmarking Methodology for Network Interconnect Devices,” March 1999.).

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] (Albanna, Z., Almeroth, K., Meyer, D., and M. Schipper, “IANA Guidelines for IPv4 Multicast Address Assignments,” August 2001.).

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] (Reynolds, J. and J. Postel, “Assigned Numbers,” October 1994.), page 4

5.  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
127.0.0.0/8         Loopback                   RFC1700, page 5
128.0.0.0/16        Subject to assignment
169.254.0.0/16      Link Local                  --
172.16.0.0/12       Private-Use Networks       RFC1918
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
224.0.0.0/4         Multicast                  RFC3171
240.0.0.0/4         Reserved for Future Use    RFC1700, page 4

6.  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] (Carpenter, B., Baker, F., and M. Roberts, “Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority,” June 2000.). Among other things, [RFC2860] (Carpenter, B., Baker, F., and M. Roberts, “Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority,” June 2000.) 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] (Carpenter, B., Baker, F., and M. Roberts, “Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority,” June 2000.) 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] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” May 2008.). 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] (Carpenter, B., Baker, F., and M. Roberts, “Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority,” June 2000.), the IANA will also make necessary experimental assignments of IPv4 addresses, also in consultation with the Regional Internet Registries.

7.  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.

8.  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.

9.  Acknowledgments

Many people have made comments on draft versions of this document. The IANA would especially like to thank Scott Bradner, Randy Bush, Leo Vegoda, and Harald Alvestrand for their constructive feedback and comments.

10.  References

10.1. Normative References

10.2. Informative References

Author's Address

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