I have a bunch of Windows 2016 servers on site at a client installation. The client has a single outgoing fiber connection and through some IPSec magic we can RDP into the server when we need to - no problem.
The client now wants us to hook up a secondary way in for emergencies, in case the first internet connection goes down. The servers are used to control some serious real world equipment, so retaining control is a good idea.
Since the location where the machines are installed is extremely remote, running another copper or fiber cable is not an option.
I got a Teltonika RUTx09 4G gateway for backup. I plugged it into the servers and was able, with port-forwarding, to connect to the RDP on all servers. I then had to remove the default gateway for the Teltonika, as the servers are communicating with some other DCOM equipment and those would no longer route.
This killed the RDP connectivity via the Teltonika. If I put the default gateway back in the config on the server on the interface connected to the Teltonika, I can connect to RDP via the Teltonika. If I remove it, I cannot. I can ping back and forth, I can visit the Teltonika web interface from the server - all connectivity appears to work, except for RDP. If I remove the default gateway, the NIC also states "unidentified network" instead of "Network 2" - but that might be unrelated.
I really cannot have the default gateway configured on the interface connected to the Teltonika and I really see no reason why RDP should not work when I can clearly communicate between server and router via any other means.
Does anyone have any insight on this?
Thanks in advance!