Unable to connect to Virtual machine suddenly via RDP through public IP

Question

Unable to connect to Virtual machine suddenly via RDP through public IP

KC Partnership 0

Hi Support team,

Unable to connect to Virtual machine suddenly via RDP through public IP.

it show error like this computer can;t connect to the remote computer, try connecting again. if the problem continue, contract the ownert of the remote computer or your network administrator.

I have restart the VM, ensure port 3389 are enabled, I have tried 3 to 4 different laptop and 2 different network and the problem still persisting. I have Reset configuration only, redeployment, Reset the NIC for the VM.

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4 answers

Your answer

Answer 1

Hi @KC Partnership

Yes, Understand your concern. first need to find the root cause. so, please follow the below steps and update to us.

tcpping <public-ip> 3389 execute this command. with your public ip. if no response VM is not rechable.
Go to: Azure Portal → VM → Boot Diagnostics If you see: Black screen Stuck at “Starting Windows” No login screen Then the VM OS is not booting correctly.
Azure Portal → VM → Serial Console If it opens, run: Reset RDP service: Code net stop termservice net start termservice Reset firewall rules: Code netsh advfirewall firewall set rule group="remote desktop" new enable=yes Re-enable RDP listener: Code reg add "HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server" /v fDenyTSConnections /t REG_DWORD /d 0 /f
If serial console not open your VM is stuck.
Azure Portal → VM → Run Command → EnableRemoteDesktop. This runs Microsoft’s built‑in RDP repair script.

Thanks.

Answer 2

Hi KC,

There's a known issue you might be running into with the September updates, last night an out of bands update was released to fix the RDP bug

Remote Desktop Services might stop responding after Sept. 2026 security update Some Windows devices with Remote Desktop enabled might experience Remote Desktop Services (RDS) instability.	OS Build 26100.9445 KB5124008 2026-09-08	Resolved KB5129195	2026-09-14 10:57 PT
for Windows 11

Remote Desktop Services might stop responding after Sept. 2026 security update Some Windows devices with Remote Desktop enabled might experience Remote Desktop Services (RDS) instability.	OS Build 26100.33438 KB5122871 2026-09-08	Resolved KB5129235	2026-09-14 10:00 PT
for Server 2025

Answer 3

KC Partnership 0

I have tried all above troubleshooting but it does not help.

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Answer 4

Since restart, Reset configuration only, redeploy, NIC reset, multiple laptops, and multiple networks were already tried, the next supported checks are the remaining Azure RDP troubleshooting steps:

Verify Network Security Group rules again with diagnostics, not only by inspection
- In Azure, use IP flow verify to confirm whether an NSG rule is blocking traffic to the VM.
- Also review effective security rules on the NIC/subnet and confirm an inbound Allow rule for TCP 3389 exists and has higher priority than any deny rule.
Check whether the VM is reachable on the network path
- From a machine in the same network, run:
```
     Test-NetConnection -ComputerName <public-ip-or-name> -Port 3389 -InformationLevel Detailed
```
- If TcpTestSucceeded is False, the issue is still network-path related.
- If TcpTestSucceeded is True, focus on guest OS configuration or authentication.
Review VM boot diagnostics
- In the Azure portal, open the VM and review Boot diagnostics screenshot/logs.
- This can reveal startup problems that block RDP even when the VM appears running.
Check VM Resource Health
- In the VM blade, open Resource health.
- A healthy VM should show Available.
Verify routing
- Use Network Watcher Next hop or review effective routes to confirm no route is preventing traffic to or from the VM.
Confirm outbound TCP 3389 is not blocked outside Azure
- Since multiple laptops and networks were tested, this is less likely, but any on-premises firewall or local firewall still must allow outbound TCP 3389.
Check guest firewall if console access is available
- On the VM, verify Remote Desktop - User Mode (TCP-In) and Remote Desktop - User Mode (UDP-In) are enabled.
- Elevated PowerShell:
```
     Get-NetFirewallRule -DisplayGroup "Remote Desktop" | Set-NetFirewallRule -Enabled True
```
- For testing only, firewall can be temporarily disabled:
```
     Set-NetFirewallProfile -Profile Domain,Public,Private -Enabled False
```
- Risk: disabling firewall reduces protection. Re-enable it after the test.
Check DNS vs IP behavior and RDP port
- If connecting by hostname fails, try the public IP directly.
- Verify the VM is still using the default RDP port 3389. If the port was changed, connect as IP:port.
Reset the VM password if credentials may be involved
- In the Azure portal, use Reset password if there is any chance the local admin credentials are incorrect.
If all checks still fail, open a support request

The documented guidance is to open a support request after these steps if RDP issues continue.

A common Azure-specific cause when RDP suddenly stops through the public IP is that the VM no longer has a usable public IP association. If the Connect button is grayed out and there is no ExpressRoute or Site-to-Site VPN, assign a public IP to the VM NIC/IP configuration before using RDP.