IANA — Number Resources


Number Resources

IANA is responsible for global coordination of the Internet Protocol addressing systems, as well as the Autonomous System Numbers used for routing Internet traffic.

Currently there are two types of Internet Protocol (IP) addresses in active use: IP version 4 (IPv4) and IP version 6 (IPv6). IPv4 was initially deployed on 1 January 1983 and is still the most commonly used version. IPv4 addresses are 32-bit numbers often expressed as 4 octets in “dotted decimal” notation (for example, Deployment of the IPv6 protocol began in 1999. IPv6 addresses are 128-bit numbers and are conventionally expressed using hexadecimal strings (for example, 2001:0db8:582:ae33::29).

Both IPv4 and IPv6 addresses are generally assigned in a hierarchical manner. Users are assigned IP addresses by Internet service providers (ISPs). ISPs obtain allocations of IP addresses from a local Internet registry (LIR) or National Internet Registry (NIR), or from their appropriate Regional Internet Registry (RIR):

Map of RIRs

Registry Area Covered
AFRINIC Africa Region
APNIC Asia/Pacific Region
ARIN North America Region
LACNIC Latin America and some Caribbean Islands
RIPE NCC Europe, the Middle East, and Central Asia

The IANA’s role is to allocate IP addresses from the pools of unallocated addresses to the RIRs according to their needs as described by global policy and to document protocol assignments made by the IETF. When an RIR requires more IP addresses for allocation or assignment within its region, the IANA makes an additional allocation to the RIR. We do not make allocations directly to ISPs or end users except in specific circumstances, such as allocations of multicast addresses or other protocol specific needs.

IP Address Allocations

Internet Protocol Version 4 (IPv4)

Internet Protocol Version 6 (IPv6)

Autonomous System Number Allocations

Emerging Regional Internet Registries

Technical Documentation

  • RFC 4632 — Classless Inter-domain Routing (CIDR): The Internet Address Assignment and Aggregation Plan
  • RFC 1918 — Address Allocation for Private Internets
  • RFC 2050 — Internet Registry IP Allocation Guidelines
  • RFC 5735 — Special-Use IPv4 Addresses
  • RFC 5736 — IANA IPv4 Special Purpose Address Registry
  • RFC 5737 — IPv4 Address Blocks Reserved for Documentation
  • RFC 4291 — Internet Protocol Version 6 (IPv6) Addressing Architecture
  • RFC 3587 — IPv6 Global Unicast Address Format
  • RFC 3177 — IAB/IESG Recommendations on IPv6 Address Allocations to Sites
  • RFC 5156 — Special-Use IPv6 Addresses


NOTICE. The following Internet Coordination Policy is being posted

for the information of the Internet community. It contains a statement

of policy followed by the Internet Assigned Numbers Authority (IANA)

in administering the system for allocation and assignment of Internet

Protocol (IP) addresses.


document was developed through ICANN’s Address Supporting Organization

(ASO) with the assistance of APNIC, ARIN, and RIPE NCC, was recommended

by the ASO’s Address Council, and on 4 June 2001 was accepted by the ICANN Board of Directors as a statement of essential requirements

for the recognition of new Regional Internet Registries (RIRs), in

supplementation to section 9 of the ASO-Memorandum of Understanding,

and acknowledged it as a framework for consideration of applications

for recognition of new RIRs.


on this document are welcome and should be directed to comments.


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