On 3 February 2011, the Number Resource Organization (NRO) announced from Montevideo that the free pool of available IPv4 addresses was fully depleted. The warning that followed was that the last addresses held by the regional registries would be handed out within months, and that networks would have to turn to IPv6.
For Asia-Pacific the timing mattered most. APNIC, the regional registry for the region, was at the centre of the final steps.
What the rule said
The mechanism was a global policy agreed by all five regional internet registries (RIRs) and ratified by ICANN in 2009. It required that when the IANA pool reached five remaining /8 blocks, those blocks be distributed simultaneously and equally to the five RIRs.
IANA assigned addresses to the RIRs in blocks equal to 1/256th of the whole IPv4 space, each called a “/8”. On Monday, 31 January, IANA allocated two blocks to APNIC, which triggered the global policy. IANA allocated the remaining blocks on 3 February. From then on, no IPv4 addresses were available from IANA for the five RIRs.
APNIC said it had received its final /8 from IANA, 103/8. It described the five blocks as roughly 16.5 million addresses each, shared equally among the world’s five regions. The NRO’s later FAQ puts each final /8 at 16.8 million addresses. The two figures differ, so the exact number depends on the source and rounding.
What the NRO told operators
The NRO warned that each RIR would have its last full /8 plus its existing holdings to distribute. It said that depending on requests, this could last anywhere from a few weeks to many months. It added that RIRs and internet service providers would eventually have to start refusing requests for IPv4 space. The NRO called IPv6 deployment a requirement, not an option.
The NRO also stated that the internet would keep working, and IPv4 addresses already in use would continue to function. Its FAQ cautioned that in future some parts of the internet might be unreachable for users whose ISP did not provide IPv6 addresses, if a service ran on an IPv6-only network.
ARIN’s chief executive, John Curran, said that ARIN still held its last /8 and its existing inventory, and that it would keep allocating IPv4 space for as long as possible. ARIN also began publishing a daily report of its available IPv4 inventory.
Why Asia-Pacific was in focus
APNIC argued that economic growth in the region over the previous decade had accelerated IPv4 exhaustion. It pointed to low earlier broadband penetration, followed by a surge in mobile internet networks that connected millions more devices. Chief Scientist Geoff Huston said the region combined some of the world’s largest populations with its fastest-growing economies.
What happened next
The regional pools ran down in stages:
- APNIC announced that on 15 April 2011 its pool reached its final /8, the last stage of exhaustion for the Asia Pacific region.
- On 14 September 2012, the RIPE NCC began allocating from its last /8.
- LACNIC followed in June 2014.
After the April 2011 milestone, APNIC changed its policies to limit sharply the amount of address space allocated, and relied on the secondary market for remaining addresses.
Policy work continued as well. ICANN ratified a global policy proposal on post-exhaustion IPv4 allocation mechanisms by IANA on 17 May 2012.
By 2026, 15 years after the IANA announcement, the NRO still describes the IANA pool as depleted on 3 February 2011.