Adding Active Directory Users to SQL Server behind a Firewall

I ran into an issue the other day that I thought others might be interested in knowing. I built a new system and turned on Windows Firewall, then discovered that I couldn't add users from Active Directory to SQL Server. This server happens to be SQL Server 2005 w/SP3 on Windows Server 2003 R2 w/SP2, however this is not the important part. I did a little research on the ports used by SQL and Windows Server and found a bunch of information which is in a previous post, "Network Ports used by Microsoft Server Products". I ultimately decided to try a few key ports and determined that I needed to enable Port 445 for TCP traffic. Enabling TCP on Port 445 resolved my issue and I was able to add users from Active Directory once again. The port is listed under a default setting in the Windows Firewall Exceptions, it is under "File and Printer Sharing". Click on "File and Printer Sharing" and choose "Edit", then Enable Port 445. This should resolve the issue with adding Active Directory users to SQL Server.