Hello Spiceworks!
I'm back once again with another strange issue! I am trying to deploy a L2TP over IPSec VPN server via my Windows Server 2012 R2. It is behind a firewall with a static NAT setup with all the necessary ports and services being forwarded to the internal address. I know it's configured properly because I can connect to the VPN via the internet. This is all fine and dandy, but here is my issue. I was using my iPhone to test the connection and managed to successfully connect with no problem. Then I tried to connect a second device (Mac) simultaneously, but got an error saying the server did not respond. I disconnected my iPhone, waited 5 minutes, and tried the Mac, and that connected no problem. But when I tried to connect my iPhone while the Mac as connected, I got the server not responding error. I tried this on Windows, but Windows will not work at all. Windows reports "error 789: The L2TP connection attempt failed because the security layer encountered a processing error during initial negotiations with remote computer."
Has anyone ever encountered this before? Oh and I'm behind the FiOS firewall on both sides and the machine I'm using remotely is Windows 7 Pro x64 if this helps or makes a difference.
Edit: I completely exposed the server to the Internet and the server allowed all simultaneous connections. I did not get to test to see if it resolved the error 789. Although on my firewall, I was allowing 500, 1701, 4500, ESP, and AH. Is there other ports that get used to allow multiple connections in through the server?
-Justin