The day has finally arrived -- IPv4 addresses have run out. When the Internet Assigned Numbers Authority (IANA) started handing out IP addresses, they had about 4.3 billion to disperse. Sounds like a lot, right? But when you consider there are 7 billion humans on the planet, with people in developed nations needing two or more devices with an address each, you can see how this number might become depleted.
Of course, IANA anticipated this depletion and created a new flavor of IP (version 6, or iPv6) in 1995 that will allow for trillions upon trillions of addresses, thanks to its 128-bit address length (versus IPv4's 32-bit length). And IPv6 is more than just an address expansion upgrade: It includes built-in IPSec security and easier management through autoconfiguration of devices. But now that IPv4 addresses are depleted, what's a Windows network administrators to do?
Most Windows PCs and servers are IPv6-enabled
The good news is that Microsoft and others started working on implementing IPv6 quite some time ago. In 1998, Microsoft released its first trial IPv6 protocol stack for Windows 95 and 98, though its capabilities were limited. Windows 2000 saw an IPv6 Technology Preview program that was also limited in capability and is no longer supported.
Windows XP had an optional IPv6 stack, but it wasn't until Windows XP SP1 that Microsoft released a production-quality IPv6 version. XP SP2's Advanced Networking Pack added simultaneous firewall support for IPv4 and IPv6, so PCs using both protocols were protected via the same firewall. Windows Server 2003 SP1 has the same pack.
As most organizations use XP SP1 or later, they have IPv6-compatible client computers already deployed. Those with Windows Server 2003 SP1 or later have IPv6-compatible servers deployed as well. Organizations using Windows Vista or Windows 7, paired with Windows Server 2008 or later, benefit from a unified dual-layer stack. Additionally, both IPv4 and IPv6 are installed and enabled by default, and the combination of IPv6 being used on both the client and the server sides will boost networking performance and security. (Mac OS X and Linux have similarly been IPv6-enabled for about as long.)
Windows 7's IPv6 network settings.