Reserved IP Addresses
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Reserved IP Addresses

In the Internet addressing architecture, the Internet Engineering Task Force (IETF) and the Internet Assigned Numbers Authority (IANA) have reserved various Internet Protocol (IP) addresses for special purposes.[1]


There are a number of addresses with special meaning in IPv4:[1]

Special address blocks
Address block Address range Number of addresses Scope Description Software Current network[1] (only valid as source address). Private network Used for local communications within a private network.[2] Private network Shared address space[3] for communications between a service provider and its subscribers when using a carrier-grade NAT. Host Used for loopback addresses to the local host.[1] Subnet Used for link-local addresses[4] between two hosts on a single link when no IP address is otherwise specified, such as would have normally been retrieved from a DHCP server. Private network Used for local communications within a private network.[2] Private network IETF Protocol Assignments.[1] Documentation Assigned as TEST-NET-1, documentation and examples.[5] Internet Reserved.[6] Formerly used for IPv6 to IPv4 relay[7] (included IPv6 address block 2002::/16). Private network Used for local communications within a private network.[2] Private network Used for benchmark testing of inter-network communications between two separate subnets.[8] Documentation Assigned as TEST-NET-2, documentation and examples.[5] Documentation Assigned as TEST-NET-3, documentation and examples.[5] Internet In use for IP multicast.[9] (Former Class D network). Internet Reserved for future use.[10] (Former Class E network). Subnet Reserved for the "limited broadcast" destination address.[1][11]


There are a number of addresses with special meaning in IPv6:[1]

Special address blocks
Address block (CIDR) First address Last address Number of addresses Usage Purpose
::/0 :: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2128 Routing Default route.
::/128 :: 1 Software Unspecified address.
::1/128 ::1 1 Host Loopback address to the local host.
::ffff:0:0/96 ::ffff: ::ffff: 2128−96 = 232 = Software IPv4 mapped addresses.
::ffff:0:0:0/96 ::ffff:0: ::ffff:0: 232 Software IPv4 translated addresses.
64:ff9b::/96 64:ff9b:: 64:ff9b:: 232 Global Internet IPv4/IPv6 translation.[12]
100::/64 100:: 100::ffff:ffff:ffff:ffff 264 Routing Discard prefix.[13]
2001::/32 2001:: 2001::ffff:ffff:ffff:ffff:ffff:ffff 296 Global Internet Teredo tunneling.
2001:20::/28 2001:20:: 2001:2f:ffff:ffff:ffff:ffff:ffff:ffff 2100 Software ORCHIDv2.[14]
2001:db8::/32 2001:db8:: 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff 296 Documentation Addresses used in documentation and example source code.[15]
2002::/16 2002:: 2002:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2112 Global Internet The 6to4 addressing scheme (now deprecated).[6]
fc00::/7 fc00:: fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2121 Private network Unique local address.[16]
fe80::/10 fe80:: febf:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2118 Link Link-local address.
ff00::/8 ff00:: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2120 Global Internet Multicast address.

See also


  1. ^ a b c d e f g M. Cotton; L. Vegoda; R. Bonica; B. Haberman (April 2013). Special-Purpose IP Address Registries. Internet Engineering Task Force. doi:10.17487/RFC6890. BCP 153. RFC 6890. Updated by RFC 8190.
  2. ^ a b c Y. Rekhter; B. Moskowitz; D. Karrenberg; G. J. de Groot; E. Lear (February 1996). Address Allocation for Private Internets. Network Working Group. doi:10.17487/RFC1918. BCP 5. RFC 1918. Updated by RFC 6761.
  3. ^ J. Weil; V. Kuarsingh; C. Donley; C. Liljenstolpe; M. Azinger (April 2012). IANA-Reserved IPv4 Prefix for Shared Address Space. Internet Engineering Task Force (IETF). doi:10.17487/RFC6598. ISSN 2070-1721. BCP 153. RFC 6598.
  4. ^ S. Cheshire; B. Aboba; E. Guttman (May 2005). Dynamic Configuration of IPv4 Link-Local Addresses. Network Working Group. doi:10.17487/RFC3927. RFC 3927.
  5. ^ a b c J. Arkko; M. Cotton; L. Vegoda (January 2010). IPv4 Address Blocks Reserved for Documentation. Internet Engineering Task Force. doi:10.17487/RFC5737. ISSN 2070-1721. RFC 5737.
  6. ^ a b O. Troan (May 2015). B. Carpenter (ed.). Deprecating the Anycast Prefix for 6to4 Relay Routers. Internet Engineering Task Force. doi:10.17487/RFC7526. BCP 196. RFC 7526.
  7. ^ C. Huitema (June 2001). An Anycast Prefix for 6to4 Relay Routers. Network Working Group. doi:10.17487/RFC3068. RFC 3068. Obsoleted by RFC 7526.
  8. ^ S. Bradner; J. McQuaid (March 1999). Benchmarking Methodology for Network Interconnect Devices. Network Working Group. doi:10.17487/RFC2544. RFC 2544. Updated by: RFC 6201 and RFC 6815.
  9. ^ M. Cotton; L. Vegoda; D. Meyer (March 2010). IANA Guidelines for IPv4 Multicast Address Assignments. Internet Engineering Task Force. doi:10.17487/RFC5771. BCP 51. RFC 5771.
  10. ^ J. Reynolds, ed. (January 2002). Assigned Numbers: RFC 1700 is Replaced by an On-line Database. Network Working Group. doi:10.17487/RFC3232. RFC 3232. Obsoletes RFC 1700.
  11. ^ Jeffrey Mogul (October 1984). Broadcasting Internet Datagrams. Network Working Group. doi:10.17487/RFC0919. RFC 919.
  12. ^ C. Bao; C. Huitema; M. Bagnulo; M. Boucadair; X. Li (October 2010). IPv6 Addressing of IPv4/IPv6 Translators. Internet Engineering Task Force. doi:10.17487/RFC6052. RFC 6052.
  13. ^ N. Hilliard; D. Freedman (August 2012). A Discard Prefix for IPv6. Internet Engineering Task Force. doi:10.17487/RFC6666. RFC 6666.
  14. ^ J. Laganier; F. Dupont (September 2014). An IPv6 Prefix for Overlay Routable Cryptographic Hash Identifiers Version 2 (ORCHIDv2). Internet Engineering Task Force. doi:10.17487/RFC7343. RFC 7343.
  15. ^ G. Huston; A. Lord; P. Smith (July 2004). IPv6 Address Prefix Reserved for Documentation. Network Working Group. doi:10.17487/RFC3849. RFC 3849.
  16. ^ R. Hinden; B. Haberman (October 2005). Unique Local IPv6 Unicast Addresses. Network Working Group. doi:10.17487/RFC4193. RFC 4193.

External links

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