How's the stock of IPv4 addresses holding up?

North America is still in good shape, but other regions are running low

The Regional Internet Registry for North America still has more than 86 million IPv4 addresses available for allocation (as of April 15), but with the global supply of addresses beginning to dry up, demand for the new IPv6 addresses is increasing.

The American Registry for Internet Numbers, one of five Regional Internet Registries that dole out IP addresses, received 253 requests for IPv6 address space from Internet service providers in the first quarter of this year, compared with 134 requests in the last three months of 2010. It received 247 end user requests in the same period this year, compared with 103 last year.

“Network operators must recognize that depletion of IPv4 space is a looming reality and should respond to the urgent need to adopt the next generation of Internet Protocol resources (IPv6) as soon as possible,” an ARIN statement says.

Related stories:

Asia’s pool of IPv4 addresses is nearly dry

IPv4: The final farewell begins

Internet Protocol addresses are the numerical addresses used networking equipment to direct traffic over the Internet. The smaller IPv4 address space, in use since the birth of the public Internet, is nearly exhausted and a global transition to IPv6 is getting underway. IPv6 has a much larger address space and a number of new features to improve online flexibility and security.

The Internet Assigned Numbers Authority, which allocates the addresses to the world’s five Regional Internet Registries, made its final allocation of /8 IPv4 address blocks to the registries in February. The registries still have supplies of the addresses to allocate to customers, but APNIC, the Asia-Pacific region’s Internet registry, has announced that it is down to its last block of addresses, a /8 block containing 16.7 million addresses.

APNIC, the Asia Pacific Network Information Centre, is the first registry to reach this landmark, which has triggered policies for rationing the distribution of final IPv4 addresses to ensure that they are available where needed to help new networking companies enable connectivity with the users of the older protocols.

ARIN called the Asian depletion “a sharp reminder that IPv4 depletion is on the event horizon for each Regional Internet Registry.”

Although the Internet community has been talking about the inevitability of IPv4 address depletion for more than a decade, the transition to IPv6 is only now beginning to gather momentum. ARIN began doling out small allotments of the new addresses in 1999, but received no ISP requests for them until 2005. Last year the total ISP requests was 434, which is likely to be outstripped this year.

In September, the Office of Management and Budget directed civilian agencies to upgrade public facing servers and services to handle IPv6 traffic by the end of fiscal 2012. Internal IP applications and systems must be upgraded by the end of fiscal 2014.

ARIN still has IPv4 address space available, but it cannot predict how long it will last and there already have been some requests for space that could not be filled because there were not enough addresses available in contiguous blocks. As of April 15, ARIN reported that it had 5.15 /8 address blocks left.

The rate of IPv4 depletion in ARIN and the other registries will depend on a number of factors, including the number of requests for space and policies for allocating them. One effort that could extend the life of the IPv4 address pool is the return or exchange of unused addresses that already have been allocated.

“It’s inevitable that there will be organizations that will want/need IPv4 address space after the ARIN resource pool becomes depleted,” the registry said in a statement. “ARIN policy supports a number of transfer options that will allow organizations that have IPv4 addresses that they don’t need to transfer them to an organization with qualified need.”

ARIN also allows organization to be placed on a waiting list of pre-qualified recipients, so that as “recycled” address blocks become available, they can be allocated to those on the waiting list on a first-come, first-served basis, depending on the size of the available blocks.

Despite these efforts, “it is important for businesses to understand that soon, organizations that require larger contiguous blocks of address space will only be able to receive them in IPv6,” ARIN said. Contiguous address space are necessary for building out new large networks and adding customers to existing networks without putting additional burdens on the Internet routing infrastructure.

ARIN has established an IPv6 wiki for deployment information at

About the Author

William Jackson is a Maryland-based freelance writer.


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