I've setup Remote Desktop Gateway Server on Windows Server 2019 and I'm using url rewrite on my internet facing IIS server to rewrite the url to the Remote desktop gateway server. I can access the server via http and https. I get the default IIS webpage on the remote desktop gateway server. The remote desktop connection via the gateway server works from my internal network. However, when I try to connect via an external laptop running windows 10 enterprise I get the error "Your computer can't connect to the remote computer because the Remote Desktop Gateway server is temporarily unavailable. Try reconnecting later or contact your network administrator for assistance."
I have reviewed the logs on the server and the client, and on the gateway server under TerminalServices-Gateway and Operational I have event 312 "The user "user@domain", on client computer "xxx.xxx.xxx.xxx:48471" has initiated an outbound connection. This connection may not be authenticated yet. On the client side there are several errors, but I'm not exactly sure what I'm looking for.
I tried changing my firewall settings and routed port 443 directly to the gateway server and was able to login and remote desktop worked as expected. So the gateway server appears to be ok and is working, but something appears to not be working between the hand off of the IIS server that is reverse proxying things.
The one thing to note is I only installed the remote desktop gateway server, but have not installed the connection broker. Out of curiosity do I need to have that installed for this scenario to work?
If there is any specific log or error details you would like to see or I should be looking for please let me know.