SSH connection to VM timeouts repeatedly after 1-3 hours

Question

SSH connection to VM timeouts repeatedly after 1-3 hours

Varun Yadav 20

Hi,
I am running a Virtual Machine with Ubuntu as OS. and it has ssh connection open at port 22. now this connection keeps getting timed out every few hours and when I restart the VM it works fine. VM metrics do not show anything out of ordinary. How can I solve this please reply ASAP.

Markapuram Sudheer Reddy 1,670 Reputation points Microsoft External Staff

2025-04-29T11:32:42.77+00:00

Hi Varun Yadav,

In continuation to @Alex Burlachenko

Could you confirm your Ubuntu VM is disconnecting after 1–3 hours due to SSH session inactivity.

Please check resource usage of VM.

If you have any queries, please do let us know, we will help you.
Varun Yadav 20 Reputation points

2025-04-29T11:54:24.9866667+00:00

Hi, Alex and Shudheer

attached image shows the logs of VM. I do not think its disconnecting due to inactivity as it always occurred when I was working on machine. when this disconnect happened, I also tried connecting to it using the Azure portal but request freezes for some time then terminates due to timeout. For now I have updated ClientAliveInterval 300, ClientAliveCountMax 2 will post here if it this does not work.

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Markapuram Sudheer Reddy 1,670 Reputation points Microsoft External Staff

2025-04-29T11:32:42.77+00:00

Hi Varun Yadav,

In continuation to @Alex Burlachenko

Could you confirm your Ubuntu VM is disconnecting after 1–3 hours due to SSH session inactivity.

Please check resource usage of VM.

If you have any queries, please do let us know, we will help you.
Varun Yadav 20 Reputation points

2025-04-29T11:54:24.9866667+00:00

Hi, Alex and Shudheer

attached image shows the logs of VM. I do not think its disconnecting due to inactivity as it always occurred when I was working on machine. when this disconnect happened, I also tried connecting to it using the Azure portal but request freezes for some time then terminates due to timeout. For now I have updated ClientAliveInterval 300, ClientAliveCountMax 2 will post here if it this does not work.

Answer 1

Alex Burlachenko 4,550

Dear Varun,

Thank you for reaching out. SSH timeouts can occur due to idle sessions, firewall rules, or TCP/IP settings. Try to adjust SSH Timeout: Modify User's image to include:

ClientAliveInterval 300

ClientAliveCountMax 2

Then restart SSH: sudo systemctl restart sshd.

Check Azure NSG Rules: Ensure your Network Security Group (NSG) allows persistent SSH traffic. Review rules here.

Enable Boot Diagnostics: Verify VM health via Azure Boot Diagnostics.

TCP Keepalive: Enable keepalive on your client (~/.ssh/config):

ServerAliveInterval 60

For further details, refer to Azure’s SSH troubleshooting guide.

Let me know if the issue persists.

https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/linux/troubleshoot-ssh-connection


Best regards,
Alex
PS If my answer help to you, please Accept my answer.
PPS that is my answer and it is not a comment :)

Alex Burlachenko 4,550 Reputation points

2025-04-29T17:20:22.3433333+00:00

just small add https://learn.microsoft.com/en-us/troubleshoot/azure/virtual-machines/linux/troubleshoot-ssh-connection
Varun Yadav 20 Reputation points

2025-05-01T11:42:22.1566667+00:00

Hi Alex and Shudheer, Today again I am facing this issue where ssh connection is getting timed out when connecting from VS code and also when using azure platform for connection request Hangs. What should I do
Markapuram Sudheer Reddy 1,670 Reputation points Microsoft External Staff

2025-05-02T11:31:45.37+00:00

Hi Varun Yadav,

The issue can likely be related to VS Code Remote SSH extension. Try to downgrade the Remote-SSH extension to version 0.49.0. https://github.com/microsoft/vscode-remote-release/issues/2513

You can verify about creating and connecting to a virtual machine (VM) on Azure using the Visual Studio Code Remote - SSH extension. https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-ssh

Check the reference article for Visual Studio Code Remote Development extension. https://code.visualstudio.com/docs/remote/ssh

If you are running into problems with VS Code hanging while trying to connect (and potentially timing out), Please check troubleshooting tips and tricks provided here for more information. https://code.visualstudio.com/docs/remote/troubleshooting#_troubleshooting-hanging-or-failing-connections

If you have any queries, please do let us know, we will help you.
Varun Yadav 20 Reputation points

2025-05-03T10:20:37.42+00:00

Hi Markapuram,
I don't think the issue is due to extension version because when I tried to connect to VM using the Azure portal. then the request waits for infinite time and then timeouts. and ssh connection from both portal and vs code works correctly if I restart VM.

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SSH connection to VM timeouts repeatedly after 1-3 hours

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