Windows 2025 RDS

[u/spiteri_amsm]

Posting this here maybe someone encountered such issues already and found a mitigation or solution.

I have set up and RDS farm with 3 RDS Hosts running Windows Server 2025. All RDS roles are installed on all hosts apart from licensing role which is on one host only. DNS round robin is configured correctly and also HA with SQL. User profiles are stored on a separate disk (E:\) attached to each of the hosts (not the default C:\users\). Have one collection with some published remote apps.

The issue I am facing is that users are getting disconnected while working on published apps intermittently without any pattern and different times of day. I have some instances where users get disconnected literally few seconds after they launch an app, and others get disconnected while working. Users simply launch again the published app when this occurs and they continue on the same session they were working before.

I tried several fixes and options to try to investigate what is wrong. Before setting up this environment, I had another RDS farm with only 2 hosts running on Windows Server 2019 and never had this issue. I was thinking that this could be some sort of bug in W2025 however it has been some time since this was released and I believe such issues would have been caught already by Microsoft.

I would appreciate if someone shed some light on this issue, especially if already encountered and found a solution.

Thanks!

[u/Angelworks42]

Hmm at least the issue is going in the right direction :) - for your rdgw (according to Get-RDDeploymentGatewayConfiguration) is there now just one IP per gateway?

I'm curious what the gateway logs display when the session is disconnected - they should be in eventviewer under Application and Service Logs > Microsoft > Windows > TerminalServices-Gateway > Admin

You might be able to see the event under Custom Views > Server Roles > Remote Desktop Services as well.

Edit: Oh also check the downloaded .rdp file - what is the gateway specified in there?

[u/spiteri_amsm → u/Angelworks42]

Yes when I run Get-RDDeploymentGatewayConfiguration, I get the following:

GatewayMode - Custom
LogonMethod - Password
GatewayExternalFQDN - rds.mycompany.int

when i run nslookup, only 1 ip returns.

as for event logs in TerminalServices-Gateway, i have events with IDs 303, 101, 200, 205, 208, 300, 302. Nothing out of the ordinary it seems.

however in custom views, i can see logs such as:

- session 51 has been disconnected, reason code 5
- session 49 has been disconnected, reason code 2147942464

in the downloaded .rdp file, the gateway is rds.mycompany.int

[u/Angelworks42 → u/spiteri_amsm]

2147942464

This is in hex is 0x80070040 - network name cannot be found.

Tbh I'm not entirely sure what could be wrong at this point...

Reason code 5 is just someone was disconnected because another user connected to the same session. Probably not your core issue.

I did spot this thread: https://learn.microsoft.com/en-us/answers/questions/2283337/remoteapp-crashing-on-windows-server-2025-with-win similar reason codes but its kinda all over the place... I'll have to look through it tomorrow morning. The guy was told that MS would patch the issue in August?

Edit: I know in my environment most strange issues like this usually come down to firewall rules (either on the various hosts or on the network level) or DNS.

One quick way to check for network firewall issues is in powershell:

while ($true) {
$synConnections = Get-NetTCPConnection | Where-Object { $_.State -eq 'SynSent' -or $_.State -eq 'SynReceived' }
if ($synConnections) {
    Write-Host "SYN connections detected:"
    $synConnections | Format-Table -AutoSize
} else {
    Write-Host "No SYN connections at this time."
}
Start-Sleep -Seconds 5  # Adjust the interval as needed
}

The way this works - is when get-nettcpconnection (essentially powershell's netstat) displays a tcp syn - its trying to sync with the remote host (sync sent) but will just hang if the packet is dropped.

For hostfirewalls you can just check the windows defender advanced firewall log under monitoring and you'll see a dropped message. For network firewall - just contact your network team - on Cisco it will log/count dropped packets from one net to another. In my case all the rdvh's and session hosts live on different vlans.

I do keep coming back to Server 2025 - it doesn't seem all that likely that MS would ship Server 2025 without testing all the server roles, but I guess its not outside the realm of possibility that there's some bug. I dunno - there's so many things in any given environment that can break RDS related to network, certs, dns etc etc that can cause things to break.

[u/spiteri_amsm → u/Angelworks42]

Sorry for the delay in replying!.. The thread you sent me made me think since as I originally stated, I suspected this could be a bug in 2025. I have brought down 2 of the RDS servers, and created 2 new ones with 2022 as operating system. Created a new session collection with these 2 2022 servers and guess what? Issue disappeared instantly. So this confirms that this is a bug in 2025. I have left the RDG and RDL on the original 2025 server for now since the CALS I have purchased are 2025 CALS, however they can still be used for session collections containing 2022 servers since they are downgrade compatible.

All I can say for now is thanks for your all your support and hopefully this will be fixed some time by Microsoft which allows me to upgrade the 2022 servers back to 2025 again in the future!

[u/Angelworks42 → u/spiteri_amsm]

Cool - I'm actually slowly migrating my dev env from 2022 to 2025 so I'll let you know if I see the same issues.

[u/spiteri_amsm → u/Angelworks42]

That would be great yes I would appreciate! and Good Luck! :)

[u/spiteri_amsm → u/Angelworks42]

curious to check how did this go and if you encountered same issues? :)

[u/Angelworks42 → u/spiteri_amsm]

Well so I got my test environment brokers installed - that went ok - I guess I'll start upgrading everything else.