When attempting to RDP using an RDS Gateway (Windows Server 2016 or Windows Server 2019), I'm receiving 'The login attempt failed' when attempting to connect outside of the network. The gateway servers are stand alone and have the same policies which allow CONTOSO\Domain Users to log into any device. The gateways were configured to use SSL and the UDP default port (3381, I believe?).
At the same time, I'm able to use the same credentials to access RDWeb on the same server. I can also connect within the network using the RD Gateway to another client on the network. Network topology is:
Public IP -> Router (forwarding TCP/443) -> HAProxy -> RDS Gateway -> target machine.
Accessing the network internally will only bypass the router, so we hit the HAProxy -> RDS Gateway -> target machine.
The client machine attempting RDP is Windows 10 1809.
Trevor Seward
Office Apps and Services MVP
Author, Deploying SharePoint 2019
Author, Deploying SharePoint 2016
This post is my own opinion and does not necessarily reflect the opinion or view of Microsoft, its employees, or other MVPs.