RDP Shortpath for Public Networks not working under General Availability

[rstuart68]

Is anyone else struggling with getting RDP Shortpath for Public networks to work?  

Under:

Applications and Services Logs > Microsoft > Windows > RemoteDesktopServices-RdpCoreCDV > Operational 

I'm getting this error message.  

Event ID 135: The multi-transport connection finished for tunnel: 1, its transport type set to TCP: Reason Code: 4 (UDP Handshake Timeout).

I've open all the required ports and IPs on the Azure FW.  I've also tested after adding this key:

New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations" -Name ICEControl -PropertyType DWORD -Value 2

I can connect with UDP when launching an AVD session internally just not remotely. 

[#2 · Accepted solution]

I wanted to provide an update. I opened a case with MS and I have fed this information back to them.

I've been collaborating with my former boss who was also having the exact same issues in his environment. We’ve figured out how to get it working for both of us but I would not deploy it this way because it’s probably not supported. After changing the two regkeys below my session immediately switched to UDP.

The trick was simple:

o Enable RDP Shortpath for Public Networks PREVIEW
o Disable RDP Shortpath for Managed Networks

In our case this involved two steps:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services
• REG_DWORD: fUseUdpPortRedirector should be 0 or DELETED
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations
• REG_DWORD: ICEControl should be 2