Frequently Asked Questions on IPv6 adoption and IPv4 exhaustion

There have been several calls to action for organisations to plan actively for the widespread deployment of the new version of the basic Internet Protocol, IPv6, which is designed to supplement and eventually replace the 25-year-old IPv4 protocol. The Internet Society strongly supports such calls for action.

If deployment is delayed, the future growth and global connectivity of the Internet will be negatively impacted.

The information below is intended to assist in answering some of the frequently asked questions associated with exhaustion of the IPv4 address pool and the adoption of IPv6.


Is the Internet about to run out of IP address numbers?

Yes and no. For the version of the Internet Protocol that underpins the Internet today (IPv4) there is a limited amount of unused space remaining. While estimates vary, based on recent trends it is anticipated that the current pool of unallocated IPv4 addresses will be consumed sometime around 2010 - 2011.

However, an enormous amount of IP address space exists under IPv6. IPv6, in fact, was specifically designed to fix the address limitations of IPv4. IPv6 addresses have been available for allocation since 1999 and the RIRs, ICANN, ISOC and others are encouraging network operators to apply for IPv6 addresses and implement IPv6 in their networks. Refer to the following announcements from:

What is IPv6?

IPv6 is the new version of the Internet address protocol that has been developed to supplement (and eventually replace) IPv4, the version that underpins the Internet today.

Who created IPv6 and how long has IPv6 been available? Is it new?

The Internet Engineering Task Force (IETF), an international group concerned with developing technical standards that make the Internet work better first published the basic IPv6 protocol in 1998. It has since seen a number of enhancements, such as the addition of mobile IPv6 specifications (in 2004).

What happened to IPv5?

Version 5 of the IP family was an experimental protocol developed in the 1980s. IPv5 (also called the Internet Stream Protocol) was never widely deployed. Since the number 5 was already allocated, this number was not considered for the successor to IPv4. Several proposals were suggested as the IPv4 successor, and each was assigned a number. In the end, it happened that the one with version number 6 was selected.

How does IPv6 solve the problem of IPv4 address exhaustion?

Simply by having a lot more address space to uniquely identify devices that are connected to the Internet. IPv4 has a theoretical maximum of about 4 billion addresses whereas IPv6 has an unthinkable theoretical maximum: about 340 trillion, trillion, trillion addresses. In actual use, IPv6 addresses are structured for routing and other purposes and as a result the number of addresses available is effectively less, but still extremely large.

For the end user, the large amount of IPv6 address space means:

  • Home users will generally be given blocks of addresses sufficient to number multiple networks and thousands of devices. (In contrast, under IPv4, home users today typically get a single address.)
  • Enterprises and small businesses will generally be given enough to number a substantial number of networks and tens of thousands of devices; while larger sites will get significantly more.

What happens when IPv4 address pool is finally depleted?

Existing devices and networks connected to the Internet through IPv4 addresses will continue to work as they do now. In fact, IPv4-based networks are expected to co-exist with IPv6-based networks at the same time.

However, for network operators and other entities that rely on Internet numbering allocations, it will become increasingly difficult and expensive (and eventually prohibitively so) to obtain new IPv4 address space to grow their networks. The cost and complexity associated with keeping track of and managing remaining IPv4 address space efficiently will also increase.

Therefore, network operators and enterprises will need to implement IPv6 in order to ensure long-term network growth and global connectivity.

When will IPv4 addresses actually run out?

The final allocations to the Regional Internet Registries (RIR) will soon be allocated. At current rates of consumption, the RIRs IPv4 address pools are likely to be depleted in approximately one year. The U.S. likely has less than a year left before *all* new networks will have to use IPv6 address space. Ahead of that date, the Internet Society and many global IT organizations are encouraging adoption of IPv6 and sponsoring World IPv6 Day in order to ready the industry for this necessary transition.