Editing IPv6 (section)

===IPv4 address exhaustion===
{{Main|IPv4 address exhaustion}}

[[File:IPv4 address structure and writing systems-en.svg|thumb|upright=1.2|Decomposition of the dot-decimal [[IPv4 address]] representation to its binary notation]]

[[IPv4|Internet Protocol Version 4]] (IPv4) was the first publicly used version of the [[Internet Protocol]]. IPv4 was developed as a research project by the [[DARPA|Defense Advanced Research Projects Agency]] (DARPA), a [[United States Department of Defense]] [[government agency|agency]], before becoming the foundation for the [[Internet]] and the [[World Wide Web]]. IPv4 includes an addressing system that uses numerical identifiers consisting of 32 bits. These addresses are typically displayed in [[dot-decimal notation]] as decimal values of four octets, each in the range 0 to 255, or 8 bits per number. Thus, IPv4 provides an addressing capability of 2<sup>32</sup> or approximately 4.3 billion addresses. Address exhaustion was not initially a concern in IPv4 as this version was originally presumed to be a test of DARPA's networking concepts.<ref>{{cite video|title=Google IPv6 Conference 2008: What will the IPv6 Internet look like?|url=https://www.youtube.com/watch?v=mZo69JQoLb8|archive-url=https://ghostarchive.org/varchive/youtube/20211211/mZo69JQoLb8|archive-date=2021-12-11|url-status=live|time=13:35}}{{cbignore}}</ref> During the first decade of operation of the Internet, it became apparent that methods had to be developed to conserve address space. In the early 1990s, even after the redesign of the addressing system using a [[Classless Inter-Domain Routing|classless network]] model, it became clear that this would not suffice to prevent [[IPv4 address exhaustion]], and that further changes to the Internet infrastructure were needed.<ref name=rfc1752>{{cite IETF|title=The Recommendation for the IP Next Generation Protocol|rfc=1752|first=S.|last=Bradner|first2=A.|last2=Mankin|date=January 1995|publisher=[[Internet Engineering Task Force|IETF]]}}</ref>

The last unassigned top-level address blocks of 16 million IPv4 addresses were allocated in February 2011 by the [[Internet Assigned Numbers Authority]] (IANA) to the five [[regional Internet registry|regional Internet registries]] (RIRs).<ref>{{Cite web |date=3 February 2011 |title=Free Pool of IPv4 Address Space Depleted |url=https://www.nro.net/ipv4-free-pool-depleted |url-status=live |archive-url=https://web.archive.org/web/20240118044214/https://www.nro.net/ipv4-free-pool-depleted |archive-date=18 January 2024 |access-date=19 January 2022 |website=NRO.net |publisher=The Number Resource Organization |location=[[Montevideo]] }}</ref> However, each RIR still has available address pools and is expected to continue with standard address allocation policies until one {{IPaddr|/8}} [[Classless Inter-Domain Routing]] (CIDR) block remains. After that, only blocks of 1,024 addresses (/22) will be provided from the RIRs to a [[local Internet registry]] (LIR). As of April 2025, all of [[Asia-Pacific Network Information Centre]] (APNIC), the [[RIPE NCC|Réseaux IP Européens Network Coordination Centre]] (RIPE NCC), [[Latin America and Caribbean Network Information Centre]] (LACNIC), [[AFRINIC|African Network Information Centre]] (AFRINIC), and [[American Registry for Internet Numbers]] (ARIN) have reached this stage.<ref>{{Cite web |last=Rashid |first=Fahmida |date=1 February 2011 |title=IPv4 Address Exhaustion Not Instant Cause for Concern with IPv6 in Wings |url=https://www.eweek.com/networking/ipv4-address-exhaustion-not-instant-cause-for-concern-with-ipv6-in-wings/ |url-status=live |archive-url=https://archive.today/20240120181901/https://www.eweek.com/networking/ipv4-address-exhaustion-not-instant-cause-for-concern-with-ipv6-in-wings/ |archive-date=20 January 2024 |access-date=23 June 2012 |publisher=eWeek }}</ref><ref>{{Cite news |last=Ward |first=Mark |date=14 September 2012 |title=Europe hits old internet address limits |url=https://www.bbc.co.uk/news/technology-19600718 |url-status=live |archive-url=https://web.archive.org/web/20231105171900/https://www.bbc.com/news/technology-19600718 |archive-date=5 November 2023 |access-date=15 September 2012 |work=[[BBC News]] }}</ref><ref>{{Cite web |last=Huston |first=Geoff |title=IPV4 Address Report |url=https://www.potaroo.net/tools/ipv4/ |url-status=live |archive-url=https://web.archive.org/web/20240110052921/https://www.potaroo.net/tools/ipv4/ |archive-date=10 January 2024 }}</ref><ref>{{Cite web |last=AFRINIC |date=2020-01-13 |title=AFRINIC enters IPv4 Exhaustion Phase 2 |url=https://afrinic.net/20200113-afrinic-enters-ipv4-exhaustion-phase-2 |access-date=2025-04-20 |website=afrinic.net |language=en-gb}}</ref>

RIPE NCC announced that it had fully run out of IPv4 addresses on 25 November 2019,<ref>{{Cite press release |date=25 November 2019 |title=The RIPE NCC has run out of IPv4 Addresses |url=https://www.ripe.net/publications/news/about-ripe-ncc-and-ripe/the-ripe-ncc-has-run-out-of-ipv4-addresses |url-status=live |archive-url=https://web.archive.org/web/20240119220002/https://www.ripe.net/publications/news/the-ripe-ncc-has-run-out-of-ipv4-addresses/ |archive-date=19 January 2024 |access-date=26 November 2019 |publisher=[[RIPE NCC]] }}</ref> and called for greater progress on the adoption of IPv6.