Reserved IP addresses

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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]


IPv4 designates special usage or applications for various addresses or address blocks:[1][2]

Special address blocks
Address block Address range Number of addresses Scope Description– 16777216 Software Current network[3]– 16777216 Private network Used for local communications within a private network.[4]– 4194304 Private network Shared address space[5] for communications between a service provider and its subscribers when using a carrier-grade NAT.– 16777216 Host Used for loopback addresses to the local host.[3]– 65536 Subnet Used for link-local addresses[6] 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.– 1048576 Private network Used for local communications within a private network.[4]– 256 Private network IETF Protocol Assignments.[3]– 256 Documentation Assigned as TEST-NET-1, documentation and examples.[7]– 256 Internet Reserved.[8] Formerly used for IPv6 to IPv4 relay[9] (included IPv6 address block 2002::/16).– 65536 Private network Used for local communications within a private network.[4]– 131072 Private network Used for benchmark testing of inter-network communications between two separate subnets.[10]– 256 Documentation Assigned as TEST-NET-2, documentation and examples.[7]– 256 Documentation Assigned as TEST-NET-3, documentation and examples.[7]– 268435456 Internet In use for IP multicast.[11] (Former Class D network.) 256 Documentation Assigned as MCAST-TEST-NET, documentation and examples.[11][12]– 268435455 Internet Reserved for future use.[13] (Former Class E network.) 1 Subnet Reserved for the "limited broadcast" destination address.[3][14]


IPv6 assigns special uses or applications for various IP addresses:[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 (no specific route)
::/128 :: :: 1 Software Unspecified address
::1/128 ::1 ::1 1 Host Loopback address—a virtual interface that loops all traffic back to itself, the local host
::ffff:0:0/96 ::ffff: ::ffff: 2128 − 96 = 232 = 4294967296 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[15]
64:ff9b:1::/48 64:ff9b:1:: 64:ff9b:1:ffff:ffff:ffff: 280 Private internets IPv4/IPv6 translation[16]
100::/64 100:: 100::ffff:ffff:ffff:ffff 264 Routing Discard prefix[17]
2001:0000::/32 2001:: 2001::ffff:ffff:ffff:ffff:ffff:ffff 296 Global Internet Teredo tunneling[18]
2001:20::/28 2001:20:: 2001:2f:ffff:ffff:ffff:ffff:ffff:ffff 2100 Software ORCHIDv2[19]
2001:db8::/32 2001:db8:: 2001:db8:ffff:ffff:ffff:ffff:ffff:ffff 296 Documentation Addresses used in documentation and example source code[20]
2002::/16 2002:: 2002:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2112 Global Internet The 6to4 addressing scheme (deprecated)[8]
fc00::/7 fc00:: fdff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2121 Private internets Unique local address[21]
fe80::/64 from fe80::/10 fe80:: fe80::ffff:ffff:ffff:ffff 264 Link Link-local address
ff00::/8 ff00:: ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 2120 Global Internet Multicast address

See also[edit]


  1. ^ a b c 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. ^ "IANA IPv4 Special-Purpose Address Registry". IANA. 19 August 2009.
  3. ^ a b c d 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.
  4. ^ 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.
  5. ^ 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.
  6. ^ S. Cheshire; B. Aboba; E. Guttman (May 2005). Dynamic Configuration of IPv4 Link-Local Addresses. Network Working Group. doi:10.17487/RFC3927. RFC 3927.
  7. ^ 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.
  8. ^ 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.
  9. ^ C. Huitema (June 2001). An Anycast Prefix for 6to4 Relay Routers. Network Working Group. doi:10.17487/RFC3068. RFC 3068. Obsoleted by RFC 7526.
  10. ^ 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.
  11. ^ a b 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.
  12. ^ S. Venaas; R. Parekh; G. Van de Velde; T. Chown; M. Eubanks (August 2012). Multicast Addresses for Documentation. Internet Engineering Task Force. doi:10.17487/RFC6676. RFC 6676.
  13. ^ 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.
  14. ^ Jeffrey Mogul (October 1984). Broadcasting Internet Datagrams. Network Working Group. doi:10.17487/RFC0919. RFC 919.
  15. ^ 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.
  16. ^ T. Anderson (August 2017). Local-Use IPv4/IPv6 Translation Prefix. Internet Engineering Task Force. doi:10.17487/RFC8215. RFC 8215.
  17. ^ N. Hilliard; D. Freedman (August 2012). A Discard Prefix for IPv6. Internet Engineering Task Force. doi:10.17487/RFC6666. RFC 6666.
  18. ^ RFC 4680
  19. ^ 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.
  20. ^ G. Huston; A. Lord; P. Smith (July 2004). IPv6 Address Prefix Reserved for Documentation. Network Working Group. doi:10.17487/RFC3849. RFC 3849.
  21. ^ R. Hinden; B. Haberman (October 2005). Unique Local IPv6 Unicast Addresses. Network Working Group. doi:10.17487/RFC4193. RFC 4193.

External links[edit]