IPv4 exhaustion and what it means for you and your wireless LAN


The Number Resource Organization recently announced that the free pool of IP version 4 address space is now fully allocated. It’s gone.

For fun, you can see the full address allocation table at the Internet Assigned Numbers Authority (IANA) web site. This month, IANA allocated the final five /8 blocks of address space to:

Africa (,
Asia/Pacific (,
North America (,
Latin America (, and
Europe (

Each regional internet registry now has a final allocation block to hand out addresses from. Depending on the rate of requests, it may only be a few weeks before your region is out of IPv4 addresses to hand out. As an example, ARIN has about half a million /24 blocks to hand out, with a rough historica trends of allocating of about 20,000 per month.

What does this mean to you? As an end user, not much right now. Most devices are still IPv4, and can use band-aids like network address translation to work with a handful of Internet-routable addresses assigned by your service provider.

Service providers, however, are on the bleeding edge of the IPv4-to-IPv6 transition. The more devices your users have, the worse the address constraints bite. It’s particularly bad for mobile networks because there are many more smart phones switched on and using data services than laptops. Of all the interesting facts from Google’s 2010 IPv6 implementation conference, the one that stuck with me the most was that T-Mobile is expecting that 50% of their mobile data use will be IPv6 by the end of this year (see slide 5 in Cameron Byrne’s presentation).

My company has seen some demand for IPv6, and the pressures on the IPv4 address space were obvious when the company was founded. Part of the reason for designing a layer-2 forwarding solution is that it accommodates both IPv4 and IPv6 without any special architectural work. I’ve been running IPv6 on my home network for quite some time now, as have many of my visitors. Linux, MacOS, and Windows 7 all are dual-stack by default, so when you attach to my home network with any of those OSes, you are assigned IPv6 addresss by default.

As the available IPv4 address pool shrinks, network administrators need to get familiar with IPv6. As a starting point, I’d recommend setting up an account at Hurricane Electric’s (free) IPv6 tunnel broker (or one of the many similar services; use your favorite web search engine for “tunnel broker.”) Hurricane Electric will assign you a /64 IPv6 prefix from their allocation, and tunnel it over your existing IPv4 connection.

There’s also a self-certification program that provides structured experimentation. Advancing requires that you set up an IPv6 web server, receive e-mail over IPv6, and run DNS over IPv6. I ran through the program for fun, and attained the rank of “Sage” (the highest level, rewarded with a free T-shirt).

Start using IPv6 at home, if for no other reason than you want the satisfaction of going to your regional Internet registry and seeing the home page plastered with warnings of IPv4 address depletion alongside a widget that says “Your IPv6 address is…”

Matthew Gast is the Director of Product Management at Aerohive Networks. He currently serves as chair of both the Wi-Fi Alliance's security task groups, was the first chair of the Wireless Network Management Marketing task group, and is the past chair of the IEEE 802.11 revision task group.