AVD sessions are dropped and session freezez

Question

AVD sessions are dropped and session freezez

udi admin 0

Starting from a few days ago, user's sessions get disconnected or freezes. They have to close Windows App (or the old Azure Virtual Desktop), and reconnect to get back to their session. We have around 15 AVD session hosts, each hosts 9 users, and the issue is sporadic, different time on different servers. Event Viewer shows Event ID 3703 and 3277. I've already manually reinstalled SxSStack based on

https://quic.hkg1.meaqua.org/en-us/troubleshoot/azure/virtual-desktop/troubleshoot-agent#error-session-host-vms-are-stuck-in-the-upgrading-state

but we still getting the same issue.

Himanshu Shekhar 1,860 Reputation points Microsoft External Staff Moderator

2025-12-11T16:20:09.64+00:00

Hello udi admin - Thank you for reaching Microsoft QnA platform

AVD sessions disconnect across 15 session hosts due to agent connectivity failures indicated by Event IDs 3703 and 3277 in Event Viewer (Windows Logs > Application).

These events signal RD Gateway URL inaccessibility (3703) or broker endpoint issues like ENDPOINT_NOT_FOUND (3277), often from network blocks, despite prior SxSStack reinstallation. - https://quic.hkg1.meaqua.org/en-us/troubleshoot/azure/virtual-desktop/troubleshoot-agent

Verify Network Connectivity - please check firewall/proxy blocks on required AVD URLs using the Required URL Check tool, ensuring TCP 443 access to rdgateway.wvd.microsoft.com and broker endpoints (e.g., rdbroker.wvd.microsoft.com/api/health).

Run WVDAgentUrlTool.exe from C:\Program Files\Microsoft RDInfra on affected hosts to identify blocked endpoints; unblock via NSG, Azure Firewall rules, or proxy exceptions (bypass 169.254.169.254 for IMDS). Confirm no local hosts file redirects and test qwinsta.exe shows rdp-sxs in Listen state post-SxSStack fix.

Validate Agent and Registration - Review RDAgentBootLoader service status (should be Automatic/Delayed Start); restart via Restart-Service RDAgentBootLoader if stopped. Inspect registry at HKLM:\SOFTWARE\Microsoft\RDInfraAgent for valid IsRegistered=1 and blank RegistrationToken - regenerate key in Azure Portal > Host Pool > Registration key if EXPIRED_MACHINE_TOKEN appears. Uninstall/reinstall full agent stack (Agent, BootLoader, SxSStack, Geneva) on one test host, re-register, and monitor for recurrence.

Check Host Pool Health - please ensure no session limits exceeded (9 users/host nearing capacity) causing ENDPOINT_NOT_FOUND; scale VM size or reduce max sessions. Monitor Azure Monitor Insights for host diagnostics, connection latency, and utilization spikes correlating with freezes.

If FSLogix profiles dismount (check Event Viewer for VHDX errors), adjust detach policies.

Run netsh winhttp show proxy and reset if needed and increase ServicesPipeTimeout to 60000 via reg add. Collect logs (WVDAgent, MsiInstaller) and open Microsoft support ticket with qwinsta output, event XML, and network traces if unresolved.

Test client-side: disable UDP/Shortpath, check Teams optimization
Himanshu Shekhar 1,860 Reputation points Microsoft External Staff Moderator

2025-12-12T22:38:39.46+00:00
Please check for potential firewalls or proxies blocking necessary URLs.

Use the Required URL Check tool to ensure you have TCP 443 access to:

rdgateway.wvd.microsoft.com

rdbroker.wvd.microsoft.com/api/health

Run the WVDAgentUrlTool.exe from C:\Program Files\Microsoft RDInfra on affected hosts. This will help identify if there are any blocked endpoints that need to be unblocked through NSG or Azure Firewall rules.

Please check the RDAgentBootLoader service status. It should be set to Automatic/Delayed Start. If it's stopped, you can restart it using: Restart-Service RDAgentBootLoader

Check on the specific Event IDs (3703 and 3277) mentioned, which may hint at RD Gateway or broker endpoint issues. Pay attention to any other alarming messages in the logs. Ensure that no session limits are being exceeded (you have 9 users per host). You might want to scale VM sizes or reduce max sessions per host to alleviate load.

If FSLogix profiles are dismounting, check the Event Viewer for VHDX errors and adjust your detach policies as necessary also If users are connecting through clients, consider disabling UDP/Shortpath or check Teams optimization features.

Please ensure log Analytics workspace is set up to review diagnostics data.

Check if using DNS encryption software is affecting connectivity and you may want to disable that temporarily.

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Himanshu Shekhar 1,860 Reputation points Microsoft External Staff Moderator

2025-12-12T22:38:39.46+00:00

Please check for potential firewalls or proxies blocking necessary URLs.

Use the Required URL Check tool to ensure you have TCP 443 access to:

rdgateway.wvd.microsoft.com

rdbroker.wvd.microsoft.com/api/health

Run the WVDAgentUrlTool.exe from C:\Program Files\Microsoft RDInfra on affected hosts. This will help identify if there are any blocked endpoints that need to be unblocked through NSG or Azure Firewall rules.

Please check the RDAgentBootLoader service status. It should be set to Automatic/Delayed Start. If it's stopped, you can restart it using: Restart-Service RDAgentBootLoader

Check on the specific Event IDs (3703 and 3277) mentioned, which may hint at RD Gateway or broker endpoint issues. Pay attention to any other alarming messages in the logs. Ensure that no session limits are being exceeded (you have 9 users per host). You might want to scale VM sizes or reduce max sessions per host to alleviate load.

If FSLogix profiles are dismounting, check the Event Viewer for VHDX errors and adjust your detach policies as necessary also If users are connecting through clients, consider disabling UDP/Shortpath or check Teams optimization features.

Please ensure log Analytics workspace is set up to review diagnostics data.

Check if using DNS encryption software is affecting connectivity and you may want to disable that temporarily.

Answer 1

Thanks for answering!

No firewall (host-based/network Firewall) blocking connection to RD Gateway URL. Using Microsoft fabric as DNS.

WVDAgentUrlTool.exe shows all addresses are accessible.

Agents are all registered and show healthy in Pool settings.

Session host performance is normal and shows a standard workload (based on Azure performance metrics)

The issue being sporadic is not helping at all. It randomly stops communicating on random servers with rd gw.

We are using Azure Load Balancer for outgoing communications. So that's the IP address that Azure RD gW fabric sees. I thought it might help.

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AVD sessions are dropped and session freezez

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