muse @ thegovernment

Windows XP Service Pack 3 Port Forwarding Not Working After Update

My main gateway computer is powered by Windows XP home edition, and for a rather long time it was running XP Service Pack 2. I use it with Internet Connection Sharing to allow my network computers access to the internet, and to allow outside computers to access my development server by forwarding the proper ports (80, 443) to the server.

After updating from XP Service Pack 2 to XP Service Pack 3, port forwarding stopped working.

Why? As far as I can tell, the Home edition update disables port forwarding--but not in any place you can find it in the GUI. It took a minor registry change, as documented at this Microsoft Knowledge Base Article , to re-enable port forwarding.

In case the article becomes unavailable, here are the steps. Be sure to back up your registry, know what you are doing, etc. I will not be held responsible if you destroy your system!

1. Start the Registry Editor (Start Menu » Run » regedit.exe)
2. Locate the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. Set the registry value IPEnableRouter (of type REG_DWORD) to the value 1
4. Reboot

That should be all you need to re-enable port forwarding. Of course, ensure that you have your firewall exceptions and port forwarding rules set up, and that a third party security app (I'm looking at YOU, app-that-rhymes-with-McCaffine) isn't blocking the ports you desire. Good luck!