Unable to connect a instance

Question

We are unable to access a VM whereas another VM is accessible with same NSG, 8383 port is inaccessible. Need quick guidance.

Answer 1

Hi @Mahesh deshpande

I have followed below mentioned steps

1. Verify inside the VM - all steps including restarted the machine, still not working.
2. Validate Azure VM agent health - validate agent is ready.
3. Redeploy the VM - Redeployed and reapplied, no luck.

performed following steps as well, still inaccessible

• Reset Winsock - (Executed command netsh winsock reset from serial console) and restarted the machine (stop and start)
• Fix broken NIC bindings
• Re‑enable services listening on 8383.

Answer 2

Hi @Manish Deshpande , Good day, we tried all options but no luck. Earlier VM was inaccessible via port 8383, suddently it became inaccessible.
We have executed following steps1. Confirm Effective NSG Rules - Didnt work**
2. Reset RDP & Windows Firewall Using Azure Run Command -** There is no EnableRemoteDesktop command, although I tried enabling via another powershell script , it throws an error "The term 'Invoke-AzVMRunCommand' is not recognized as the name of a cmdlet, function"
3. Test RDP Connectivity via Azure Network Watcher - All green, however RDP connectivity didnt work.
4. Validate Guest OS Firewall - Validated, but VM is inaccessible.
5. Accessing VM from another VM - Didnt work, attached screenshot

Answer 3

Hello Anindya Pal

This behavior typically occurred due to one or more of the following inside the affected VM, even when NSG rules were correct:

1. Windows Firewall blocking port 3389
2. RDP service (TermService) stopped or hung
3. NIC-level NSG Association mismatch
4. Guest OS network stack corruption
5. VM routing issue resolved by redeploy

Steps to perform :

1.Confirm Effective NSG Rules :

Even if the NSG is shared, validate effective rules on the NIC.

Azure Portal → VM → Networking → Effective security rules

• Ensure Inbound TCP 3389 = Allow
• Check no higher‑priority Deny rule exists

2.Reset RDP & Windows Firewall Using Azure Run Command :

This step resolved the issue in most previously reported cases.

Azure Portal → VM → Run command → EnableRemoteDesktop

This action:

• Re‑enables RDP
• Resets Windows Firewall rules for 3389
• Restarts required services.

3.Test RDP Connectivity via Azure Network Watcher :

**Confirms whether traffic reaches the VM NIC.

Network Watcher → Connection troubleshoot

• Destination port: 3389
• Result should show Reachable

4.Redeploy the VM:

If RDP is still failing, VM redeploy has resolved several identical cases by resetting:

• Host networking
• Hypervisor routing
• Underlying fabric issues

Azure Portal → VM → Redeploy + reapply(Left Pane)

Redeploy does not delete disks but causes VM downtime.

5.Validate Guest OS Firewall :

If Serial Console / Bastion is available:

• Ensure firewall rule allows TCP 3389
• Confirm Remote Desktop Services is running. Links:
  https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/windows/troubleshoot-rdp-connection

https://learn.microsoft.com/en-us/azure/network-watcher/connection-troubleshoot-manage?tabs=portal

https://learn.microsoft.com/en-us/azure/virtual-machines/windows/run-command?tabs=portal%2Cpowershellremove

Thanks,
Manish Deshpande.

Answer 4

Follow https://learn.microsoft.com/en-us/azure/virtual-network/troubleshoot-vm-connectivity . Check OS level firewall

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hth

Marcin