IPv4 address exhaustion

IPv4 address exhaustion is the depletion of the pool of unallocated Internet Protocol Version 4 (IPv4) addresses, which has been anticipated since the late 1980s. This depletion is the reason for the development and deployment of its successor protocol, IPv6.

The IP address space is managed by the Internet Assigned Numbers Authority (IANA) globally, and by five regional Internet registries (RIR) responsible in their designated territories for assignment to end users and local Internet registries, such as Internet service providers. The top-level exhaustion occurred on 31 January 2011. Four of the five RIRs have exhausted allocation of all the blocks they have not reserved for IPv6 transition; this occurred on 15 April 2011 for the Asia-Pacific, on 14 September 2012 for Europe, on 10 June 2014 for Latin America and the Caribbean, and on 24 September 2015 for North America.

IPv4 provides approximately 4.3 billion addresses; a subset of these have been distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each. The depletion of the IPv4 allocation pool has been a concern since the late 1980s, when the Internet started to experience dramatic growth. The Internet Engineering Task Force (IETF) created the Routing and Addressing Group (ROAD) in November 1991 to respond to the scalability problem caused by the classful network allocation system in place at the time. The anticipated shortage has been the driving factor in creating and adopting several new technologies, including network address translation (NAT), Classless Inter-Domain Routing (CIDR) in 1993, and IPv6 in 1998. IPv6, the successor technology to IPv4 which was designed to address this problem, supports approximately 7038340000000000000♠3.4×10³⁸ network addresses.