DNS Works but SSH Connection Still Fails with 'Could Not Resolve Hostname' on First Attempt Then Starts to Work After a Few Seconds

Have you ever encountered an issue where you are trying to establish an SSH connection to a remote server, but it fails with the error message 'Could Not Resolve Hostname' on the first attempt? Don't worry, you are not alone! This issue can be quite frustrating, but fortunately, there is a common solution.

The error message 'Could Not Resolve Hostname' indicates that your computer is unable to translate the hostname of the remote server into its corresponding IP address. This translation is done by the DNS (Domain Name System) server. So, if your DNS is working correctly, why does the SSH connection still fail on the first attempt?

The reason behind this issue lies in the way SSH handles DNS resolution. When you initiate an SSH connection, your computer tries to resolve the hostname using DNS. However, if the DNS response is not received within a certain time frame, SSH assumes that the hostname is invalid and fails the connection.

This issue is more likely to occur when you are using a slow or unreliable internet connection. The DNS response may take longer to reach your computer, causing the initial failure. But don't worry, there is a simple workaround to resolve this problem.

The solution is to configure SSH to wait for a longer period before giving up on the DNS resolution. This can be done by modifying the SSH configuration file, which is usually located at /etc/ssh/sshd_config.

Follow these steps to modify the SSH configuration:

1. Open the SSH configuration file using a text editor. You might need administrative privileges to make changes to this file.
2. Find the line that starts with #UseDNS and remove the '#' symbol to uncomment the line.
3. Change the value of UseDNS to no. It should now look like UseDNS no.
4. Save the changes and exit the text editor.

By setting UseDNS to no, you are instructing SSH not to perform DNS resolution. This means that SSH will skip the DNS resolution step and directly use the IP address of the remote server for the connection.

After making these changes, try establishing an SSH connection again. You should notice that the connection no longer fails with the 'Could Not Resolve Hostname' error message on the first attempt. SSH will now directly use the IP address, allowing the connection to be established successfully.

It is important to note that disabling DNS resolution in SSH may have some implications. For example, if the IP address of the remote server changes frequently, you may need to manually update the SSH configuration each time. However, in most cases, this workaround should resolve the issue without any negative consequences.

Hopefully, this article has helped you understand why your SSH connection was failing with the 'Could Not Resolve Hostname' error message on the first attempt. By modifying the SSH configuration to disable DNS resolution, you can establish the connection successfully without any delays.