I have an odd situation whereby I can RDP onto my terminal server and main server internally, so RDP is working and enabled, However when trying to connect externally from another location, the connection fails. I get the standard error (Remote Desktop can't connect to the remote computer for one of the following reasons:.....) the same as if you had mistyped the address. I am however able to connect to the main server from an external location.
Here are the facts:
Nat rule set for main server to port forward 3390 to 192.168.1.1 on internal port 3389
Nat rule set for TERMINAL server to port forward 3389 to 192.168.1.2 on internal port 3389
Connection to remote.company.com:3390 (or external static IP) to main sbs server WORKS
Connection to remote.company.com:3389 (or external static IP) to Terminal Server DOES NOT
All connections onsite using internal host names and local IP addresses work.
Router NAT rules: SWAP the local IP addresses between the two servers round. See if the internal IP was being blocked. No change. Checked with external port checker and the termserver always shows as blocked, regardless of the port or internal IP used.
Completely removed all NAT rules on the DrayTek firewall/router and re-created
Installed NEW router with NAT rules present
Created a completely new virtual network adapter with a different IP address on the Terminal Server
Changed the internal port within the registry from 3389 to 3391
Turned off ALL firewall rules on router and completely disabled the firewall on Terminal server
Re-created RDP connection in TS configuration
Stopped all Sophos AV and firewall services
Checked startup icons in MSconfig - nothing untoward
Scanned with Malware Bytes and rougue killer, delete 5 items but no change - also uninstalled a number of unusual program that have been installed.
Checked for any strange processes running that could be blocking access (odd software firewall etc) - nothing untoward
Reboot on a number of occasions during the above troubleshooting processes.
Short of re-installing the operating system, I am at a loss as to what else I can try.