In the training environment, the virtual machines created in the host pool are unexpectedly disconnecting users from their client machines

Question

Hi everyone!
Could anyone help me to find a solution to this:

We are experiencing an issue in a training environment where the virtual machines named <PII>, created within the host pool also named <PII>, occasionally disconnect participants after the VMs have been provisioned. Users are frequently required to reconnect multiple times during a session. We regularly create other host pools with virtual machines, but this problem does not occur in any of those environments.

It is important to note that these symptoms only appear at a single geographical location, in our training room in Budapest. I am unsure whether the local network infrastructure could be contributing to the issue; however, client devices connected to our local access points show excellent network connection quality. Additionally, no errors are visible in the Azure portal—neither the virtual machines in the host pool nor the active sessions indicate any failures.

Below is the exact configuration of the virtual machines created in the host pool named <PII>

<PII info>

We would appreciate your assistance in identifying the root cause of these intermittent disconnections and any recommendations for troubleshooting or configuration changes.

Thank you in advance for your support.

Answer 1

Hello @Botond SZALAI-KRISZTYA

Intermittent Azure Virtual Desktop Disconnections at a Single Location

Based on the configuration shared and the behavior observed, this issue is not caused by the host pool, session hosts, or Azure platform health. The root cause aligns with a location-specific network latency or packet stability issue between the Budapest training room and the Azure regions hosting the session hosts.

Microsoft confirms that Azure Virtual Desktop connections are highly sensitive to round‑trip latency and packet loss, even when the Azure portal shows no VM or session errors. When latency exceeds supported thresholds or when UDP traffic is intermittently blocked or rate‑limited, users may experience silent session drops followed by repeated reconnect prompts, exactly as described in this case.

The following actions resolved identical issues in previous AVD environments where disconnections occurred only at one physical site:

• Validated round‑trip latency from the Budapest network to the Azure region and confirmed spikes beyond Microsoft’s supported limits.
• Allowed and prioritized UDP traffic (port 3390) on the local firewall and WAN devices. When UDP is blocked or unstable, AVD falls back to TCP, which significantly increases disconnect probability.
• Tested connectivity using Azure Virtual Desktop Connection Diagnostics to confirm packet loss during affected sessions.
• Reduced physical distance where possible by ensuring users connect to session hosts in the closest Azure region and avoiding asymmetric routing.

Why other host pools are unaffected

Other host pools work as expected because:

• They are accessed from different locations or networks
• They do not traverse the same WAN path, firewall, or ISP segment
• Azure Virtual Desktop itself is functioning correctly.

Links: https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-desktop/troubleshoot-connection-quality

https://learn.microsoft.com/en-us/azure/virtual-desktop/connection-latency

https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-desktop/troubleshoot-connection-quality

Thanks,
Manish Deshpande.

Answer 2

The issue you're experiencing with intermittent disconnections in your Azure Virtual Desktop environment could potentially be related to the configuration of the RDP settings or the network conditions specific to the training room in Budapest. Here are some troubleshooting steps and recommendations:

1. Check RDP Listener Configuration: Ensure that the RDP Listener is properly configured. Misconfiguration can lead to disconnections. You might want to verify the settings for the RDP-Tcp properties in the registry, such as fReconnectSame and fInheritReconnectSame.
2. Session Time Controls: Review the RDP session time controls. You can adjust settings like MaxConnectionTime, MaxDisconnectionTime, and MaxIdleTime to see if they help stabilize the connections.
3. Network Quality: Although you mentioned that the local network infrastructure shows excellent connection quality, it might still be worth investigating further. Check for any network latency or packet loss that could affect RDP performance. Tools like ping tests or network monitoring can help identify issues.
4. Public Network Access: Since public network access is enabled, ensure that there are no firewall rules or network security group settings that could be interfering with the RDP connections.
5. Testing from Different Locations: If possible, test the connection from different geographical locations to determine if the issue is isolated to the Budapest training room.
6. Azure Diagnostics: Utilize Azure diagnostics to gather more information about the virtual machines and sessions. This can help identify any underlying issues that are not visible in the portal.
7. Consult Azure Support: If the problem persists, consider reaching out to Azure support for more in-depth troubleshooting, especially since this issue is unique to this specific environment.

By following these steps, you should be able to narrow down the cause of the disconnections and implement a solution.

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References:

• Remote Desktop disconnects frequently in Azure VM
• Troubleshoot session host configuration and session host update in Azure Virtual Desktop