This works fine as long as you are only connected to one network at a time. As a matter of fact, more and more users now have their own networks at home. The problem is that once they connect to the corpnet, the Domain firewall rule set becomes active, which will break homegroup connections. The solution to this problem seems to be to work with multiple NICs. However, in Windows Vista, only one profile can be active on the computer at a time. Windows Sever 2008 machines that are connected to multiple networks suffer the same problem. In this case, the profile with the most restrictive settings is applied to all adapters on the computer.
Windows-7-Firewall-Protected-Connections Windows 7′s multiple active firewall profiles are the solution to this problem. It is now possible to assign each firewall profile to specific NICs.
Quelle: Windows 7 multiple active firewall profiles - 4sysops