In February of 2011, the Internet Assigned Numbers Authority (IANA) allocated its final two /8 IPv4 address blocks of address space. That event marked the end of the so called "free pool" availability of IPv4 address space available to Regional Internet Registries (RIR), but it didn't mean that IPv4 had become unavailable.
Now in April of 2014, ARIN (American Registry for Internet Numbers) is announcing that it is down to the final /8 of available space in its own inventory. ARIN manages IP address space allocations for the U.S., Canada and Caribbean regions. ARIN is one of five global Regional Internet Registry (RIR) organizations that in turn receive their IP allocations from the Internet Assigned Numbers Authority (IANA).
"ARIN may experience situations where it can no longer fulfill qualifying IPv4 requests due to a lack of inventory of the desired block size," Leslie Nobile, director, Registration Services at ARIN, wrote in a statement.
Back in 2010, ARIN explained to Internet News how the final allocations for IPv4 would occur. It's a multi-stage process that involves increasingly smaller size limits on the addresses available for Internet service providers' requests.
Each IPv4 /8 block contains 16,777,214 addresses. ARIN is now down to its final /8 allocation. ARIN can choose to give out IPv4 allocations in smaller blocks, which include a /10 allocation of 4 million addresses or a /15 allocation of 131,000 addresses.
"All IPv4 requests will be processed on a 'First in, First out' basis, and all requests of any size will be subject to team review, and requests for /15 or larger will require department director approval," Nobile stated.
IPv4 only has a total of 4.3 billion addresses globally, though many enterprises and data centers are able to leverage Network Address Translation (NAT) to enable multiple private IPs to use one public IPv4 address.
In contrast, the IPv6 address space, which is the next generation of IP addressing, provides 340 trillion trillion trillion (34 x 10 to the 38th power) Internet addresses. Though IPv4 addresses have been dwindling for years, widespread IPv6 adoption has been slow to date.
Sean Michael Kerner is a senior editor at Enterprise Networking Planet and InternetNews.com. Follow him on Twitter @TechJournalist.