Special Use IPv4 Addresses
draft-iana-rfc3330bis-01

Status of this Memo

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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.

Table of Contents

1.  Introduction
2.  Terminology
3.  Global and Other Specialized Address Blocks
4.  Summary Table
5.  Assignments of IPv4 Blocks for New Specialized Uses
6.  IANA Considerations
7.  Security Considerations
8.  Acknowledgments
9.  References
    9.1.  Normative References
    9.2.  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 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] (Carpenter, B., Baker, F., and M. Roberts, “Memorandum of Understanding Concerning the Technical Work of the Internet Assigned Numbers Authority,” June 2000.)]. Section 4 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.  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.

14.0.0.0/8 - This block was set aside for assignments to the international system of Public Data Networks [[RFC1700] (Reynolds, J. and J. Postel, “Assigned Numbers,” October 1994.), page 181]. All the assignments made for this purpose were reclaimed by the IANA And 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.

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] (Internet Assigned Numbers Authority (IANA), “Class A Subnet Experiment,” April 1995.)]. 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] (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. 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.

191.255.0.0/16 - This block, corresponding to the numerically highest to 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.

192.0.0.0/24 - This block, corresponding to the numerically lowest of the former Class C 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.

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.)].

223.255.255.0/24 - This block, corresponding to the numerically highest of the former Class C 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 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] (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]

4.  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          Subject to allocation
24.0.0.0/8          Cable Television Networks
39.0.0.0/8          Subject to allocation
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
191.255.0.0/16      Subject to allocation       --
192.0.0.0/24        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    Subject to allocation       --
224.0.0.0/4         Multicast                  RFC3171
240.0.0.0/4         Reserved for Future Use    RFC1700, page 4

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] (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.

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 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.

8.  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.

9.  References

9.1. Normative References

9.2. Informative References

Author's Address

Full Copyright Statement

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