I want to setup a VPN server with OpenVPN, so client PCs can access each other like they were in the same physical network.
One problem I encountered is, that I cannot connect via UDP. When I change server+client configuration to use TCP connections, clients can successfully connect to the server. I read TCP over TCP is bad and incurs a lot of overhead.
The server is behind a router with a public IP and the server's IP is configured to be in the DMZ of the router.
Is there a way I can test where the connection fails when using UDP? At the client's router, at the client's ISP, at my router, somewhere else? Is such a setup even possible with UDP or do I have to resort to TCP?
If I missed essential details, let me know and I'll be happy to add them.