KB 937168 - After you configure Internet Connection Sharing in Windows Vista, the network connection stops working after one-to-two hours.

SYMPTOMS

After you configure Internet Connection Sharing in Windows Vista, you may find that, although the network connection works correctly at first, the network connection stops working after one-to-two hours. For example, you may be unable to connect to the Internet, to other computers on the local area network (LAN), or to network resources on the LAN.

CAUSE

This problem occurs because of a bug in the WinSock bind() function.

A little backstory

I have a long and sordid history with this bug. I don't remember encountering it with the pre-RTM Vista builds but I also didn't push my systems like I do now.

When I am at a customer site, just as a good policy, I keep my work laptop off their network unless I specifically need access, with approval of course. I will use my Motorola Q as my data connection to the internet through Bluetooth on my Thinkpad. I am a bit of a virtual machine junkie, so I will fire up various virtual machines in either VMWare or Virtual PC.

I have always used the Loopback network device to give my internet access to my virtual machines. I typically will enable ICS (Internet Connection Sharing) on whatever device has the internet connection and assign the sharing to the Loopback adapter. I know there are many other ways to do this, but this always works well for me.

I have a script that I run that connects to an SSH server in a loop, in case the connection drops. I could use something like AutoSSH but my simple script works just as well for what I need.

Typically after 15 minutes to 4 hours, I know this bug has triggered because most pre-existing network connections are still active and working, but any new network connection errors out with a very puzzling "Permission denied".

At that point, my SSH script will go into an infinite loop. The only decent way to get rid of the error, before this hotfix, was to reboot the laptop.

With this patch installed, I can stay connected al day until I have to go home.

A quick sidenote: You can easily add the Loopback adapter in Vista by right clicking the computer name and selecting Add legacy hardware in Device Manager.