Address allocation kicks off IPv4 endgame

Two new allocations will force the last big address blocks to be assigned

The Internet Assigned Numbers Authority has assigned two large blocks of IPv4 addresses to the Asia-Pacific Network Information Centre, activating a rule under which the agency will give out the last of its IPv4 addresses.

[ See also: IPv6 basics: Getting started with IPv6 ]

The rule states that when only five large blocks of IP addresses remain, one will be handed out to each of the world's five regional Internet registries. With the latest allocation to APNIC, the number of remaining IP address blocks is down to five.

IANA is expected to assign the remaining blocks within a matter of days or less. After that, the regional bodies will have no higher source of addresses to turn to when they have assigned the addresses they hold.

IPv4's address space allows for only about 4.3 billion unique Internet addresses, which client and server computers use to connect with the Internet. The remaining IPv4 addresses have been dwindling over the past few years. The latest version of Internet Protocol, IPv6, has a nearly unlimited number of addresses but is not yet widely used.

As expected, APNIC, the regional Internet registry for Asia, has requested and been assigned two "/8" -- or "slash-8" -- address blocks, each of which contains about 16 million IP addresses. The newly assigned blocks are 39/8 and 106/8, which as recently as last week were unallocated. Now only 102/8, 103/8, 179/8 and 185/8 remain unallocated. Some other /8 blocks are reserved for special purposes such as multicasting.

p>After IANA has allocated the last of its addresses to the regional registries, Internet service providers (ISPs) and enterprises will still be able to get addresses from those registries until they run out. An IANA official said last week that he believes ISPs are accelerating their requests for addresses as the supply nears its end.

APNIC expects to continue its own normal address allocations for three to six months, according to an advisory it posted Monday to a Cisco user mailing list. After that time, the organization will start making assignments from its last block according to a policy designed to make sure enough IPv4 addresses are available for the transition to IPv6. Under that policy, each APNIC account holder will only be eligible for one minimum-sized address allocation.

The organization expects those allocations to continue for about five years. During that time, APNIC will hold one smaller /16 block in reserve for unforeseen future needs.

APNIC was allowed to request the two blocks assigned on Monday because of the fast rate at which it had been handing out addresses. In the past 14 days, APNIC's available address space declined from 1.79 of the large /8 blocks to 1.22.

"APNIC reiterates that IPv6 is the only means available for the sustained ongoing growth of the Internet, and urges all members of the Internet industry to move quickly towards its deployment," APNIC said in its advisory.

However, there are potential pitfalls both in migrating to IPv6 and trying to maintain a connection to Internet resources under IPv4 after new sites are forced to use IPv6.

(Additional reporting by Robert McMillan in San Francisco.)

Stephen Lawson covers mobile, storage and networking technologies for The IDG News Service. Follow Stephen on Twitter at @sdlawsonmedia. Stephen's e-mail address is

Copyright © 2011 IDG Communications, Inc.

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