IPv4 Address Exhaustion

IPv4 address exhaustion is the depletion of the pool of unallocated Internet Protocol Version 4 (IPv4) addresses. 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. With IANA's exhaustion on 31 January 2011, the exhaustion of the RIRs APNIC on 15 April 2011 and RIPE NCC on 14 September 2012, some parts of the world have already exhausted their IPv4 allocations, and the remaining RIRs are expected to deplete their pools within a few years.

IPv4 provides approximately 4.29 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 Classless Inter-Domain Routing (CIDR) in 1993, network address translation (NAT), and IPv6 in 1998; IPv6 (Internet Protocol Version 6), which can support about 3.4×1038 addresses, is the IETF's successor technology to IPv4.

Although the predicted depletion was already approaching its final stages in 2008, most providers of Internet services and software vendors were just beginning IPv6 deployment.