IPv4 address exhaustion and the move to IPv6

Updated November 2026

IPv4 has room for about 4.3 billion addresses, and the free supply ran out in stages between 2011 and 2020. Networks now stretch IPv4 with address sharing (NAT and carrier-grade NAT) and buy addresses on a transfer market, while IPv6 slowly takes over: on November 1, 2026, about half of Google’s users reached it over IPv6.

Why IPv4 ran out

An IPv4 address is 32 bits long, so there are 232 = 4,294,967,296 possible addresses. Large chunks are reserved for private networks, multicast and other special uses, and early allocations were generous: a single /8 block holds 224 = 16,777,216 addresses. With billions of phones, computers and servers, demand passed supply.

Addresses flow down a chain. IANA gives large blocks to the five Regional Internet Registries (RIRs), and they assign space to ISPs and other organizations in their region.

The run-out dates

On February 3, 2011, IANA made its final allocations. Under a global policy agreed by all five RIR communities and ratified in 2009, the last five /8 blocks went one to each RIR. Each registry then ran down its own pool at its own pace, usually keeping a “last /8” for small, rationed allocations to newcomers.

IPv4 run-out milestones by registry
RegistryRegionMilestone
APNICAsia-PacificReached its final /8 on April 15, 2011
RIPE NCCEurope, Middle East, Central AsiaReached its last /8 in September 2012; ran out completely on November 25, 2019
LACNICLatin America, CaribbeanFinal phase from February 2017; announced on August 28, 2020 that it had reserved its last available block
ARINNorth America (US, Canada, parts of the Caribbean)Free pool depleted on September 24, 2015
AFRINICAfricaExhaustion phase 1 from March 31, 2017; phase 2 from January 13, 2020 (allocations of /24 to /22 only)

“Ran out” does not mean nobody can get IPv4. Registries keep waiting lists filled from returned and reclaimed space; at the RIPE NCC, for example, an organization can wait for a single /24 (256 addresses). And addresses can be bought and sold: ARIN, for instance, approves transfers between organizations under its transfer policies, with pre-approval valid for 24 months.

NAT: sharing addresses

Network address translation lets many devices share one public address. Your home router gives each device a private address (such as 192.168.1.20 from the 192.168.0.0/16 range) and rewrites outgoing packets to use the router’s one public address, keeping a table of which connection belongs to which device.

Carrier-grade NAT (CGNAT) does the same thing one level up, inside the ISP: many customers share a pool of public addresses. RFC 6598 (April 2012) reserved 100.64.0.0/10 as “shared address space” for the links between the ISP’s NAT and customers’ routers, so it does not clash with the private ranges people use at home. If your router’s outside address starts with 100.64 to 100.127, you are almost certainly behind CGNAT.

NAT works for browsing, but it has costs:

IPv6

IPv6, now specified in RFC 8200 (July 2017, Internet Standard STD 86), uses 128-bit addresses: 2128, about 3.4 × 1038. A single /64 subnet alone holds 264 addresses, so every device can have its own globally reachable address again and NAT is not needed. Other changes matter for measurement: every IPv6 link must carry packets of at least 1,280 bytes, and routers never fragment packets; only the sender does, which makes path MTU discovery essential.

How far adoption has come

Google publishes the share of its users who reach it over IPv6. Read on November 3, 2026, the data showed:

The figure swings within each week, between about 45% and 51% in the second half of October 2026, and is consistently higher on weekends than on weekdays, so compare like with like. Countries differ widely. Google’s per-country native IPv6 figures as of November 1, 2026, included France 86.3%, Germany 75.7%, India 68.9%, Japan 57.2%, Brazil 56.1%, the United States 54.7%, the United Kingdom 54.6% and China 7.1%.

Check your own connection

ip -6 addr show scope global      # do you have a global IPv6 address?
ping -6 -c 4 www.google.com       # can you reach an IPv6 host?
tracepath -6 www.google.com       # path and MTU over IPv6
curl -6 -sI https://www.google.com/

If the first command prints nothing, your network has not given you IPv6; ask your ISP whether it is offered. If you run servers, give them IPv6 addresses and AAAA records so IPv6-only and CGNAT users can reach them directly.

Sources