HomeGroup: A practical guide to domestic bliss with Windows 7
 

An important thing to understand is that HomeGroup requires IPv6 to be operational on your local network. This is enabled in Windows 7 by default, and you don't need any special routing equipment to support it. A lot of people are still unfamiliar with IPv6, but using it on a local network is both completely safe and easy to understand. When you connect a Windows 7 (or any other IPv6-supporting operating system) to a local network, a "link-local IPv6 address" is calculated by the computer for that network. No "DHCPv6" server is required. Link-local IPv6 addresses are easy to identify (they start with fe80) and no IPv6 router will route traffic to or from those addresses. In other words, they work the same way as the 169.254.x.x range of addresses in IPv4. HomeGroup is designed so that it can only communicate on link-local IPv6 addresses, and only on networks that you've denoted as a "Home network."

http://arstechnica.com/microsoft/gui...campaign=r ss