For the Wikipedia user access level, see Wikipedia:User access levels#Unregistered users
An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing.
Internet Protocol version 4 (IPv4) defines an IP address as a 32-bit number. However, because of the growth of the Internet and the depletion of available IPv4 addresses, a new version of IP (IPv6), using 128 bits for the IP address, was developed in 1995, and standardized as RFC 2460 in 1998.IPv6 deployment has been ongoing since the mid-2000s.
IP addresses are usually written and displayed in human-readable notations, such as 172.16.254.1 in IPv4, and 2001:db8:0:1234:0:567:8:1 in IPv6. The size of the routing prefix of the address is designated in CIDR notation by suffixing the address with the number of significant bits, e.g., 192.168.1.15/24, which is equivalent to the historically used subnet mask 255.255.255.0.
The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA), and by five regional Internet registries (RIRs) responsible in their designated territories for assignment to end users and local Internet registries, such as Internet service providers. IPv4 addresses have been distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each. Each ISP or private network administrator assigns an IP address to each device connected to its network. Such assignments may be on a static (fixed or permanent) or dynamic basis, depending on its software and practices.
An IP address serves two principal functions. It identifies the host, or more specifically its network interface, and it provides the location of the host in the network, and thus the capability of establishing a path to that host. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there." The header of each IP packet contains the IP address of the sending host, and that of the destination host.
Two versions of the Internet Protocol are in common use in the Internet today. The original version of the Internet Protocol for use in the Internet is Internet Protocol version 4 (IPv4), first deployed in 1983.
The rapid exhaustion of IPv4 address space available for assignment to Internet service providers and end user organizations by the early 1990s, prompted the Internet Engineering Task Force (IETF) to explore new technologies to expand the addressing capability in the Internet. The result was a redesign of the Internet Protocol which became eventually known as Internet Protocol Version 6 (IPv6) in 1995. IPv6 technology was in various testing stages until the mid-2000s, when commercial production deployment commenced.
Today, these two versions of the Internet Protocol are in simultaneous use. Among other technical changes, each version defines the format of addresses differently. Because of the historical prevalence of IPv4, the generic term IP address typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of version 5 to the experimental Internet Stream Protocol in 1979, which however was never referred to as IPv5.
Main article: IPv4 § Addressing
An IPv4 address has a size of 32 bits, which limits the address space to 4294967296 (232) addresses. Of this number, some addresses are reserved for special purposes such as private networks (~18 million addresses) and multicast addressing (~270 million addresses).
IPv4 addresses are usually represented in dot-decimal notation, consisting of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., 172.16.254.1. Each part represents a group of 8 bits (octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.
In the early stages of development of the Internet Protocol, network administrators interpreted an IP address in two parts: network number portion and host number portion. The highest order octet (most significant eight bits) in an address was designated as the network number and the remaining bits were called the rest field or host identifier, and were used for host numbering within a network.
This early method soon proved inadequate as additional networks developed that were independent of the existing networks already designated by a network number. In 1981, the Internet addressing specification was revised with the introduction of classful network architecture.
Classful network design allowed for a larger number of individual network assignments and fine-grained subnetwork design. The first three bits of the most significant octet of an IP address were defined as the class of the address. Three classes (A, B, and C) were defined for universal unicast addressing. Depending on the class derived, the network identification was based on octet boundary segments of the entire address. Each class used successively additional octets in the network identifier, thus reducing the possible number of hosts in the higher order classes (B and C). The following table gives an overview of this now obsolete system.
|Size of network|
number bit field
|Size of rest|
|Start address||End address|
|A||0||8||24||128 (27)||16,777,216 (224)||0.0.0.0||127.255.255.255|
|B||10||16||16||16,384 (214)||65,536 (216)||126.96.36.199||188.8.131.52|
|C||110||24||8||2,097,152 (221)||256 (28)||192.0.0.0||184.108.40.206|
Classful network design served its purpose in the startup stage of the Internet, but it lacked scalability in the face of the rapid expansion of the network in the 1990s. The class system of the address space was replaced with Classless Inter-Domain Routing (CIDR) in 1993. CIDR is based on variable-length subnet masking (VLSM) to allow allocation and routing based on arbitrary-length prefixes.
Today, remnants of classful network concepts function only in a limited scope as the default configuration parameters of some network software and hardware components (e.g. netmask), and in the technical jargon used in network administrators' discussions.
Early network design, when global end-to-end connectivity was envisioned for communications with all Internet hosts, intended that IP addresses be uniquely assigned to a particular computer or device. However, it was found that this was not always necessary as private networks developed and public address space needed to be conserved.
Computers not connected to the Internet, such as factory machines that communicate only with each other via TCP/IP, need not have globally unique IP addresses. Three non-overlapping ranges of IPv4 addresses for private networks were reserved in RFC 1918. These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry.
Today, when needed, such private networks typically connect to the Internet through network address translation (NAT).
|Start||End||Number of addresses|
Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of 192.168.0.0 through 192.168.0.255 (192.168.0.0/24).
Main article: IPv6 address
In IPv6, the address size was increased from 32 bits in IPv4 to 128 bits or 16 octets, thus providing up to 2128 (approximately 7038340299999999999♠3.403×1038) addresses. This is deemed sufficient for the foreseeable future.
The intent of the new design was not to provide just a sufficient quantity of addresses, but also redesign routing in the Internet by more efficient aggregation of subnetwork routing prefixes. This resulted in slower growth of routing tables in routers. The smallest possible individual allocation is a subnet for 264 hosts, which is the square of the size of the entire IPv4 Internet. At these levels, actual address utilization ratios will be small on any IPv6 network segment. The new design also provides the opportunity to separate the addressing infrastructure of a network segment, i.e. the local administration of the segment's available space, from the addressing prefix used to route traffic to and from external networks. IPv6 has facilities that automatically change the routing prefix of entire networks, should the global connectivity or the routing policy change, without requiring internal redesign or manual renumbering.
The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated for efficient routing. With a large address space, there is no need to have complex address conservation methods as used in CIDR.
All modern desktop and enterprise server operating systems include native support for the IPv6 protocol, but it is not yet widely deployed in other devices, such as residential networking routers, voice over IP (VoIP) and multimedia equipment, and network peripherals.
Just as IPv4 reserves addresses for private networks, blocks of addresses are set aside in IPv6. In IPv6, these are referred to as unique local addresses (ULA). RFC 4193 reserves the routing prefix fc00::/7 for this block which is divided into two /8 blocks with different implied policies. The addresses include a 40-bit pseudorandom number that minimizes the risk of address collisions if sites merge or packets are misrouted.
Early practices used a different block for this purpose (fec0::), dubbed site-local addresses. However, the definition of what constituted sites remained unclear and the poorly defined addressing policy created ambiguities for routing. This address type was abandoned and must not be used in new systems.
Addresses starting with fe80:, called link-local addresses, are assigned to interfaces for communication on the attached link. The addresses are automatically generated by the operating system for each network interface. This provides instant and automatic communication between all IPv6 host on a link. This feature is required in the lower layers of IPv6 network administration, such as for the Neighbor Discovery Protocol.
Private address prefixes may not be routed on the public Internet.
IP networks may be divided into subnetworks in both IPv4 and IPv6. For this purpose, an IP address is logically recognized as consisting of two parts: the network prefix and the host identifier, or interface identifier (IPv6). The subnet mask or the CIDR prefix determines how the IP address is divided into network and host parts.
The term subnet mask is only used within IPv4. Both IP versions however use the CIDR concept and notation. In this, the IP address is followed by a slash and the number (in decimal) of bits used for the network part, also called the routing prefix. For example, an IPv4 address and its subnet mask may be 192.0.2.1 and 255.255.255.0, respectively. The CIDR notation for the same IP address and subnet is 192.0.2.1/24, because the first 24 bits of the IP address indicate the network and subnet.
IP address assignment
IP addresses are assigned to a host either dynamically at the time of booting, or permanently by fixed configuration of the host hardware or software. Persistent configuration is also known as using a static IP address. In contrast, when a computer's IP address is assigned newly each time it restarts, this is known as using a dynamic IP address.
The configuration of a static IP address depends in detail on the software or hardware installed in the computer. Computers used for the network infrastructure, such as routers and mail servers, are typically configured with static addressing, Static addresses are also sometimes convenient for locating servers inside an enterprise.
Dynamic IP addresses are assigned using methods such as Zeroconf for self-configuration, or by the Dynamic Host Configuration Protocol (DHCP) from a network server. The address assigned with DHCP usually has an expiration period, after which the address may be assigned to another device, or to the originally associated host if it is still powered up. A network administrator may implement a DHCP method so that the same host always receives a specific address.
DHCP is the most frequently used technology for assigning addresses. It avoids the administrative burden of assigning specific static addresses to each device on a network. It also allows devices to share the limited address space on a network if only some of them are online at a particular time. Typically, dynamic IP configuration is enabled by default in modern desk top operating systems. DHCP is not the only technology used to assign IP addresses dynamically. Dialup and some broadband networks use dynamic address features of the Point-to-Point Protocol.
In the absence or failure of static or stateful (DHCP) address configurations, an operating system may assign an IP address to a network interface using state-less auto-configuration methods, such as Zeroconf.
Sticky dynamic IP address
A sticky dynamic IP address is an informal term used by cable and DSL Internet access subscribers to describe a dynamically assigned IP address which seldom changes. The addresses are usually assigned with DHCP. Since the modems are usually powered on for extended periods of time, the address leases are usually set to long periods and simply renewed. If a modem is turned off and powered up again before the next expiration of the address lease, it often receives the same IP address.
RFC 3330 defines an address block 169.254.0.0/16 for the special use in link-local addressing for IPv4 networks. In IPv6, every interface, whether using static or dynamic address assignments, also receives a local-link address automatically in the block fe80::/10.
These addresses are only valid on the link, such as a local network segment or point-to-point connection, that a host is connected to. These addresses are not routable and like private addresses cannot be the source or destination of packets traversing the Internet.
When the link-local IPv4 address block was reserved, no standards existed for mechanisms of address autoconfiguration. Filling the void, Microsoft created an implementation that is called Automatic Private IP Addressing (APIPA). APIPA has been deployed on millions of machines and has, thus, become a de facto standard in the industry. In RFC 3927, the IETF defined a formal standard for this functionality, entitled Dynamic Configuration of IPv4 Link-Local Addresses.
An IP address conflict occurs when two devices on the same local physical or wireless network claim to have the same IP address. A second assignment of an address generally stops the IP functionality of one or both of the devices. Many modern operating systems notify the administrator of IP address conflicts. If one of the devices is the gateway, the network will be crippled. When IP addresses are assigned by multiple people and systems with differing methods, any of them may be at fault.
IP addresses are classified into several classes of operational characteristics: unicast, multicast, anycast and broadcast addressing.
The most common concept of an IP address is in unicast addressing, available in both IPv4 and IPv6. It normally refers to a single sender or a single receiver, and can be used for both sending and receiving. Usually, a unicast address is associated with a single device or host, but a device or host may have more than one unicast address. Some individual PCs have several distinct unicast addresses, each for its own distinct purpose. Sending the same data to multiple unicast addresses requires the sender to send all the data many times over, once for each recipient.
Main article: Broadcasting (computing)
In IPv4 it is possible to send data to all possible destinations ("all-hosts broadcast"), which permits the sender to send the data only once, and all receivers receive a copy of it. In the IPv4 protocol, the address 255.255.255.255 is used for local broadcast. In addition, a directed (limited) broadcast can be made by combining the network prefix with a host suffix composed entirely of binary 1s. For example, the destination address used for a directed broadcast to devices on the 192.0.2.0/24 network is 192.0.2.255. IPv6 does not implement broadcast addressing and replaces it with multicast to the specially-defined all-nodes multicast address.
A multicast address is associated with a group of interested receivers. In IPv4, addresses 220.127.116.11 through 18.104.22.168 (the former Class D addresses) are designated as multicast addresses. IPv6 uses the address block with the prefix ff00::/8 for multicast applications. In either case, the sender sends a single datagram from its unicast address to the multicast group address and the intermediary routers take care of making copies and sending them to all receivers that have joined the corresponding multicast group.
Like broadcast and multicast, anycast is a one-to-many routing topology. However, the data stream is not transmitted to all receivers, just the one which the router decides is logically closest in the network. Anycast address is an inherent feature of only IPv6. In IPv4, anycast addressing implementations typically operate using the shortest-path metric of BGP routing and do not take into account congestion or other attributes of the path. Anycast methods are useful for global load balancing and are commonly used in distributed DNS systems.
A host may use geolocation software to deduce the geolocation of its communicating peer.
A public IP address, in common parlance, is a globally routable unicast IP address, meaning that the address is not an address reserved for use in private networks, such as those reserved by RFC 1918, or the various IPv6 address formats of local scope or site-local scope, for example for link-local addressing. Public IP addresses may be used for communication between hosts on the global Internet.
For security and privacy considerations, network administrators often desire to restrict public Internet traffic within their private networks. The source and destination IP addresses contained in the headers of each IP packet are a convenient means to discriminate traffic by IP address blocking or by selectively tailoring responses to external requests to internal servers. This is achieved with firewall software running on the networks gateway router. A database of IP addresses of permissible traffic may be maintained in blacklists or whitelists.
Multiple client devices can appear to share an IP address, either because they are part of a shared hostingweb server environment or because an IPv4 network address translator (NAT) or proxy server acts as an intermediary agent on behalf of the client, in which case the real originating IP address might be masked from the server receiving a request. A common practice is to have a NAT mask a large number of devices in a private network. Only the "outside" interface(s) of the NAT needs to have an Internet-routable address.
Commonly, the NAT device maps TCP or UDP port numbers on the side of the larger, public network to individual private addresses on the masqueraded network.
In residential networks, NAT functions are usually implemented in a residential gateway. In this scenario, the computers connected to the router have private IP addresses and the router has a public address on its external interface to communicate on the Internet. The internal computers appear to share one public IP address.
Computer operating systems provide various diagnostic tools to examine their network interface and address configuration. Windows provides the command-line interface tools ipconfig and netsh and users of Unix-like systems can use ifconfig, netstat, route, lanstat, fstat, or iproute2 utilities to accomplish the task.
- ^ abcRFC 760, DOD Standard Internet Protocol (January 1980)
- ^ abRFC 1883, Internet Protocol, Version 6 (IPv6) Specification, S. Deering, R. Hinden (December 1995)
- ^ abRFC 2460, Internet Protocol, Version 6 (IPv6) Specification, S. Deering, R. Hinden, The Internet Society (December 1998)
- ^ abInternet Protocol – DARPA Internet Program Protocol Specification. September 1981. doi:10.17487/RFC0791. RFC 791. https://tools.ietf.org/html/rfc791.
- ^Address Allocation for Private Internets. IETF. February 1996. p. 4. doi:10.17487/RFC1918. RFC 1918. https://tools.ietf.org/html/rfc1918#page-4.
- ^RFC 4193 section 3.2.1
- ^RFC 3513
- ^RFC 3879
- ^"Event ID 4198 — TCP/IP Network Interface Configuration". Microsoft. 7 January 2009. Archived from the original on 24 December 2013. Retrieved 2 June 2013. "Updated: January 7, 2009"
- ^"Event ID 4199 — TCP/IP Network Interface Configuration". Microsoft. 7 January 2009. Archived from the original on 22 December 2013. Retrieved 2 June 2013. "Updated: 7 January 2009"
- ^Mitchell, Bradley. "IP Address Conflicts – What Is an IP Address Conflict?". About.com. Archived from the original on 13 April 2014. Retrieved 23 November 2013.
- ^Kishore, Aseem (4 August 2009). "How to Fix an IP Address Conflict". Online Tech Tips Online-tech-tips.com. Archived from the original on 25 August 2013. Retrieved 23 November 2013.
- ^"Get help with "There is an IP address conflict" message". Microsoft. 22 November 2013. Archived from the original on 26 September 2013. Retrieved 23 November 2013.
- ^"Fix duplicate IP address conflicts on a DHCP network". Microsoft. Archived from the original on 28 December 2014. Retrieved 23 November 2013. Article ID: 133490 – Last Review: 15 October 2013 – Revision: 5.0
- ^Moran, Joseph (1 September 2010). "Understanding And Resolving IP Address Conflicts - Webopedia.com". Webopedia.com. Archived from the original on 2 October 2013. Retrieved 23 November 2013.
- ^RFC 5771
- ^"IP Information". 11 April 2013. Archived from the original on 4 July 2013. Retrieved 11 April 2013.
- ^"NetAcuity Edge Offers Hyper-local IP targeting". 28 July 2009. Archived from the original on 5 February 2012. Retrieved 10 December 2011.
- ^Comer, Douglas (2000). Internetworking with TCP/IP:Principles, Protocols, and Architectures – 4th ed. Upper Saddle River, NJ: Prentice Hall. p. 394. ISBN 0-13-018380-6. Archived from the original on 13 April 2010.
Some large /8 blocks of IPv4 addresses, the former Class A network blocks, are assigned in whole to single organizations or related groups of organizations, either by the Internet Corporation for Assigned Names and Numbers (ICANN), through the Internet Assigned Numbers Authority (IANA), or a regional Internet registry.
Each /8 block contains 224 = 16,777,216 addresses.
As IPv4 address exhaustion has advanced to its final stages, some organizations, such as Stanford University, formerly using 22.214.171.124/8 (now to APNIC) have returned their allocated blocks to assist in the delay of the exhaustion date.
List of reserved /8 blocks
See also Reserved IP addresses
List of assigned /8 blocks
|Block||Organization||IANA date||RIR date||Notes|
|126.96.36.199/8||Level 3 Communications, Inc.||1992-12||1992-12-01||Originally Bolt Beranek and Newman Inc. (then GTE, then Genuity) 1992-12.|
Updated to Level 3 Communications, Inc. in 2007-04.
|188.8.131.52/8||Level 3 Communications, Inc.||1992-12||1992-12-01||Originally Bolt Beranek and Newman Inc. (then GTE, then Genuity) 1992-12.|
Updated to Level 3 Communications, Inc. in 2007-04.
|184.108.40.206/8||AT&T Services||1995-06||1983-08-23||Originally AT&T Bell Laboratories, retained by AT&T when Bell Labs was spun off to Lucent Technologies in 1996.|
|220.127.116.11/8||Hewlett-Packard Company||1994-11||1989-05-18||Digital Equipment Corporation, then Compaq, then Hewlett-Packard; now known as Hewlett Packard Enterprise and HP Inc.|
|18.104.22.168/8||Ford Motor Company||1995-05||1988-06-15|
|22.214.171.124/8||PSINet, Inc.||1994-09||1991-04-16||PSINet, then Cogent Communications.|
|126.96.36.199/8||Amateur Radio Digital Communications||1992-07||1992-07-01|
|188.8.131.52/8||Prudential Securities Inc.||1995-05||1990-12-07||The Prudential Insurance Company of America.|
|184.108.40.206/8||US Postal Service||1994-06||1992-11-02|
List of assigned /8 blocks to the United States Department of Defense
List of assigned /8 blocks to the Regional Internet Registries
The Regional Internet Registries (RIR) allocate IPs within a particular region of the world.
|Block||Organization||IANA date||RIR date||Notes|
|220.127.116.11/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
|18.104.22.168/8||RIPE NCC||2009-10||Formerly IANA - Reserved 1981-09.|
|22.214.171.124/8||ARIN||1994-05||Various Registries (Maintained by ARIN). Formerly General Electric Company.|
|126.96.36.199/8||RIPE NCC||2010-11||Formerly IANA - Reserved 1995-07.|
|188.8.131.52/8||ARIN||1992-08||Various Registries (Maintained by ARIN). Formerly IBM.|
|184.108.40.206/8||ARIN||1991-09||Various Registries (Maintained by ARIN).|
|220.127.116.11/8||APNIC||2010-04||Starting 1991-06-01, was used to map Public Data Network (X.121) addresses to IP addresses. Returned to IANA 2008-01-22. This network was reclaimed by IANA in 2007 and was subsequently re-allocated in 2010. See RFC 877 and RFC 1356 for historical information.|
|18.104.22.168/8||ARIN||1991-09||Various Registries (Maintained by ARIN). Formerly Hewlett-Packard Company.|
|22.214.171.124/8||ARIN||1994-01||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||ARIN||1994-10||Various Registries (Maintained by ARIN). Formerly DXC Technology. Computer Sciences Corporation, who owned this block, merged with HP Enterprise Services to create DXC Technology on 3 April 2017.|
|188.8.131.52/8||ARIN||2010-11||Formerly IANA - Reserved 1995-07.|
|184.108.40.206/8||ARIN||2001-05||2001-05-01||Formerly IANA - Cable Block 1995-07, then ARIN - Cable Block 2001-05. Updated to ARIN not before 2007.|
|220.127.116.11/8||RIPE NCC||1995-01||As of 2005-08-23 entire block assigned to UK Ministry of Defence|
|18.104.22.168/8||APNIC||2010-01||Formerly IANA - Reserved 1995-04.|
|22.214.171.124/8||RIPE NCC||2010-05||2010-05-18||Formerly IANA - Reserved 1991-04.|
|126.96.36.199/8||ARIN||1994-06||Various Registries (Maintained by ARIN). Formerly AT&T Global Network Services. Originally Norsk Informasjonsteknologi (at that time maintained by RIPE NCC). IBM acquired Norsk Informasjonsteknologi (Norway) in 1995.|
|188.8.131.52/8||ARIN||1993-03||Various Registries (Maintained by ARIN). Formerly Halliburton Company.|
|184.108.40.206/8||ARIN||1994-04||2012-08||Various Registries (Maintained by ARIN). Formerly Merit Network 1986.|
|220.127.116.11/8||APNIC||2010-10||Formerly Stanford University 1993-04, then IANA - Reserved 2000-07.|
|18.104.22.168/8||RIPE NCC||2010-11||Formerly IANA - Reserved 1995-04.|
|22.214.171.124/8||APNIC||2011-01||Formerly IANA - Reserved 1995-04.|
|126.96.36.199/8||ARIN||1994-06||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||AFRINIC||2005-04||Formerly IANA - Reserved 1995-05.|
|184.108.40.206/8||APNIC||2010-10||Formerly IANA - Reserved 1995-07.|
|220.127.116.11/8||APNIC||1991-01||1989-02-21||Various Registries (Maintained by APNIC). Originally Japan Inet 1991-01 (IANA date) or 1989-02-21 (RIR date). Administered by APNIC not before 2007.|
|18.104.22.168/8||ARIN||1995-01||1991-09-09||Various Registries (Maintained by ARIN). Formerly Interop Show Network 1995-01 or 1991-09-09 (RIR date). Returned to ARIN in 2010-10 except a /15 block. In 2011 it became available for distribution (or possibly be returned to the IANA, depending on the global policy in effect at that time).|
|22.214.171.124/8||RIPE NCC||2009-09||Formerly Bolt Beranek and Newman Inc. 1992-12. Returned to IANA in 2007-04. Updated to IANA - Reserved in 2007-04.|
|126.96.36.199/8||ARIN||1991-01||Various Registries (Maintained by ARIN). Formerly Bell-Northern Research.|
|188.8.131.52/8||APNIC||2010-08||Formerly Joint Technical Command (Returned to IANA Mar 98) 1994-05. Updated to IANA - Reserved in 2007-05.|
|184.108.40.206/8||ARIN||2010-02||Formerly Joint Technical Command (Returned to IANA Mar 98) 1994-05. Updated to IANA - Reserved in 2007-05.|
|220.127.116.11/8||RIPE NCC||1994-08||Various Registries (Maintained by RIPE NCC). Formerly UK Government Department for Work and Pensions.|
|18.104.22.168/8||RIPE NCC||1993-10||As of some date before 2015-05-05 the entire block assigned to Daimler AG.|
|22.214.171.124/8||ARIN||1992-03||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||RIPE NCC||1995-05||Formerly SITA.|
|188.8.131.52/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
|184.108.40.206/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
|220.127.116.11/8||RIPE NCC||2010-01||Formerly IANA - Reserved 1981-09.|
|18.104.22.168/8||ARIN||2010-11||100.64.0.0/10 reserved for [rfc:6598 Shared Address Space (RFC 6598]).|
|22.214.171.124/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
|126.96.36.199/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
|188.8.131.52/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
|184.108.40.206/8||ARIN||1993-05||Various Registries (Maintained by ARIN). 220.127.116.11 is the start address of formerly "Class B".|
|18.104.22.168/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|22.214.171.124/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|184.108.40.206/8||APNIC||1997-03||Various Registries (Maintained by APNIC).|
|220.127.116.11/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|18.104.22.168/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|22.214.171.124/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|184.108.40.206/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|220.127.116.11/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|18.104.22.168/8||RIPE NCC||1993-05||Various Registries (Maintained by RIPE NCC).|
|22.214.171.124/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|184.108.40.206/8||RIPE NCC||1993-05||Various Registries (Maintained by RIPE NCC).|
|220.127.116.11/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|18.104.22.168/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|22.214.171.124/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||APNIC||1993-05||Various Registries (Maintained by APNIC).|
|184.108.40.206/8||RIPE NCC||1993-05||Various Registries (Maintained by RIPE NCC).|
|220.127.116.11/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|18.104.22.168/8||APNIC||1993-05||Various Registries (Maintained by APNIC).|
|22.214.171.124/8||AFRINIC||1993-05||Various Registries (Maintained by AFRINIC).|
|126.96.36.199/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|184.108.40.206/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|220.127.116.11/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|18.104.22.168/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|22.214.171.124/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|184.108.40.206/8||APNIC||1993-05||Various Registries (Maintained by APNIC).|
|220.127.116.11/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|18.104.22.168/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|22.214.171.124/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|126.96.36.199/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|188.8.131.52/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|184.108.40.206/8||ARIN||1993-05||1993-05-01||Various Registries (Maintained by ARIN). 169.254.0.0/16 (169.254.0.0–169.254.255.255) reserved for link-local addressing (RFC 6890).|
|220.127.116.11/8||ARIN||1993-05||Various Registries (Maintained by ARIN).|
|18.104.22.168/8||APNIC||1993-05||Various Registries (Maintained by APNIC).|
|22.214.171.124/8||ARIN||1993-05||1993-05-01||Various Registries (Maintained by ARIN). 172.16.0.0/12 (172.16.0.0–172.31.255.255) reserved for private networks (RFC 1918).|
|126.96.36.199/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
|188.8.131.52/8||RIPE NCC||1993-05||Various Registries (Maintained by RIPE NCC).|
|184.108.40.206/8||LACNIC||1993-05||Various Registries (Maintained by LACNIC).|
|192.0.0.0/8||ARIN||1993-05||1993-05-01||Various Registries (Maintained by ARIN). 192.0.2.0/24 reserved for TEST-NET-1 (RFC 5737). 220.127.116.11/24 reserved for 6to4 Relay Anycast (RFC 3068). 192.168.0.0/16 (192.168.0.0–192.168.255.255) reserved for private networks (RFC 1918). 192.0.0.0/24 reserved for IANA IPv4 Special Purpose Address Registry (RFC 5736). 192.0.0.0 is the start address of formerly "Class C".|
|18.104.22.168/8||AFRINIC||1993-05||Various Registries (Maintained by AFRINIC).|
|22.214.171.124/8||ARIN||1993-05||Various Registries (Maintained by ARIN). 198.18.0.0/15 reserved for Network Interconnect Device Benchmark Testing (RFC 6890). 198.51.100.0/24 reserved for TEST-NET-2 (RFC 5737).|
|126.96.36.199/8||APNIC||2009-10||188.8.131.52/19 transferred to AFRINIC|
|184.108.40.206/8||APNIC||1993-05||203.0.113.0/24 reserved for TEST-NET-3 (RFC 5737).|
|220.127.116.11/8||APNIC||2010-01||Formerly IANA - Reserved 1981-09.|
Note that this list may not include current assignments of /8 blocks to all regional or national Internet registries.
Original list of IPv4 assigned address blocks
The original list of IPv4 address blocks can be found in RFC 790 (Postel, J., September 1981). In a previous version of the document, RFC 776 (Postel, J., January 1981), network numbers were 8-bit numbers rather than the 32-bit numbers used in IPv4. RFC 790 also added three networks not listed in RFC 776: 42.rrr.rrr.rrr, 43.rrr.rrr.rrr, and 44.rrr.rrr.rrr.
The relevant portion of RFC 790 is reproduced here with minor changes:
- 000.rrr.rrr.rrr Reserved [JBP]
- 001.rrr.rrr.rrr BBN-PR BBN Packet Radio Network [DCA2]
- 002.rrr.rrr.rrr SF-PR-1 SF Packet Radio Network [JEM]
- 003.rrr.rrr.rrr BBN-RCC BBN RCC Network [SGC]
- 004.rrr.rrr.rrr SATNET Atlantic Satellite Network [DM11]
- 005.rrr.rrr.rrr SILL-PR Ft. Sill Packet Radio Network[JEM]
- 006.rrr.rrr.rrr SF-PR-2 SF Packet Radio Network [JEM]
- 007.rrr.rrr.rrr CHAOS MIT CHAOS Network [MOON]
- 008.rrr.rrr.rrr CLARKNET SATNET subnet for Clarksburg [DM11]
- 009.rrr.rrr.rrr BRAGG-PR Ft. Bragg Packet Radio Net [JEM]
- 010.rrr.rrr.rrr ARPANET ARPANET [VGC]
- 011.rrr.rrr.rrr UCLNET University College London [PK]
- 012.rrr.rrr.rrr CYCLADES CYCLADES [VGC]
- 013.rrr.rrr.rrr Unassigned [JBP]
- 014.rrr.rrr.rrr TELENET TELENET [VGC]
- 015.rrr.rrr.rrr EPSS British Post Office EPSS [PK]
- 016.rrr.rrr.rrr DATAPAC DATAPAC [VGC]
- 017.rrr.rrr.rrr TRANSPAC TRANSPAC [VGC]
- 018.rrr.rrr.rrr LCSNET MIT LCS Network [DDC2]
- 019.rrr.rrr.rrr TYMNET TYMNET [VGC]
- 020.rrr.rrr.rrr DC-PR D.C. Packet Radio Network [VGC]
- 021.rrr.rrr.rrr EDN DCEC EDN [EC5]
- 022.rrr.rrr.rrr DIALNET DIALNET [MRC]
- 023.rrr.rrr.rrr MITRE MITRE Cablenet [APS]
- 024.rrr.rrr.rrr BBN-LOCAL BBN Local Network [SGC]
- 025.rrr.rrr.rrr RSRE-PPSN RSRE / PPSN [BD2]
- 026.rrr.rrr.rrr AUTODIN-II AUTODIN II [EC5]
- 027.rrr.rrr.rrr NOSC-LCCN NOSC / LCCN [KTP]
- 028.rrr.rrr.rrr WIDEBAND Wide Band Satellite Network [CJW2]
- 029.rrr.rrr.rrr DCN-COMSAT COMSAT Dist. Comp. Network [DLM1]
- 030.rrr.rrr.rrr DCN-UCL UCL Dist. Comp. Network [PK]
- 031.rrr.rrr.rrr BBN-SAT-TEST BBN SATNET Test Network [DM11]
- 032.rrr.rrr.rrr UCL-CR1 UCL Cambridge Ring 1 [PK]
- 033.rrr.rrr.rrr UCL-CR2 UCL Cambridge Ring 2 [PK]
- 034.rrr.rrr.rrr MATNET Mobile Access Terminal Net [DM11]
- 035.rrr.rrr.rrr NULL UCL/RSRE Null Network [BD2]
- 036.rrr.rrr.rrr SU-NET Stanford University Ethernet [MRC]
- 037.rrr.rrr.rrr DECNET Digital Equipment Network [DRL]
- 038.rrr.rrr.rrr DECNET-TEST Test Digital Equipment Net [DRL]
- 039.rrr.rrr.rrr SRINET SRI Local Network [GEOF]
- 040.rrr.rrr.rrr CISLNET CISL Multics Network [CH2]
- 041.rrr.rrr.rrr BBN-LN-TEST BBN Local Network Testbed [KTP]
- 042.rrr.rrr.rrr S1NET LLL-S1-NET [EAK]
- 043.rrr.rrr.rrr INTELPOST COMSAT INTELPOST [DLM1]
- 044.rrr.rrr.rrr AMPRNET Amateur Radio Experiment Net [HM]