How to Fix kex_exchange_identification: connection closed by remote host

I recently encountered an issue connecting to a remote server via SSH. I got the following error message: “kex_exchange_identification: connection closed by remote host.” After some research and troubleshooting, I could fix the issue and successfully connect to the server.

In this article, I will share my steps to fix the “kex_exchange_identification: connection closed by remote host” error.

Causes of the Error kex_exchange_identification: connection closed by remote host

Before diving into the fix, it’s important to understand what this error message is telling us. The “kex” in the error message stands for “key exchange,” which is the process of securely exchanging keys between the client (in this case, our computer) and the server.

The “exchange identification” part of the message refers to the initial identification exchange between the client and server.

The “connection closed by remote host” part of the message tells us that the server closed the connection before completing the key exchange and identification process. This can happen for various reasons, including incorrect login credentials, a firewall blocking the connection, or a problem with the server’s SSH configuration.

Related: Fix: SSH could not resolve hostname

How to Fix kex_exchange_identification: connection closed by remote host

Solution 1: Check Your Login Credentials

The first step in troubleshooting this error is to ensure you are using the correct login credentials for the server. Double-check your username and password to ensure that they are correct.

Solution 2: Check if the Server is Down

Sometimes the server may be down or offline for maintenance. Try connecting to the server later to see if the issue has been resolved.

Solution 3: Check Your Internet Connection

A weak or unstable internet connection can cause issues connecting to a remote server. Ensure your internet connection is stable and you can connect to other websites or servers.

Solution 3: Check for Existing ssh-keys

If you have already added ssh-keys to the remote server, try to connect with ssh -v option, it will give you more details about the connection process. If the remote server is not accepting your key, you should check if the key is still valid and authorized on the remote server.

• Enable the verbose option with SSH by running this command in your Terminal:

ssh -v hostname

Check the output for any indication of any errors.

Solution 4: Check the Server’s SSH Configuration

The server’s SSH configuration can also cause the “kex_exchange_identification: connection closed by remote host” error.

If you have access to the SSH server (SSHD), you can run this command on the server:

sudo /usr/sbin/sshd -t

The -t option checks the SSH configuration file for errors and if it is valid.

Solution 5: Check Your Firewall Settings

A firewall can block the connection between your computer and the server. Check your firewall settings to ensure it is not blocking the connection.

How to Fix kex_exchange_identification: connection closed by remote host

Based on the troubleshooting steps above, here are some solutions to try if you’re still experiencing the “kex_exchange_identification: connection closed by remote host” error:

1. Use the correct login credentials. Make sure that you are using the correct login credentials for the server. Double-check your username and password to ensure that they are correct.
2. Reconfigure SSH on the server. If the server’s SSH configuration is causing the issue, contact the server administrator to reconfigure SSH on the server.
3. Add your public key to the server. If the server is not accepting your key, you can try to upload your public key again to the server.
4. Try connecting from another network or computer. If the issue is related to your network or computer, try connecting to the server from a different network or computer to see if the issue persists.
5. Check the firewall settings. If a firewall is blocking the connection, check your firewall settings to ensure it is not blocking the connection. You can try temporarily disabling the firewall to test the connection and re-enable it after it is successful. Contact your network administrator if you cannot access the firewall settings.
6. Check for any updates or patches. Sometimes, updates or patches to the server or SSH software can fix the “kex_exchange_identification: connection closed by remote host” error. Check for any updates or patches and apply them if necessary.
7. Try using a different SSH client. If you are using a specific SSH client and are still experiencing the error, try using a different SSH client to see if that resolves the issue.

Conclusion

By following the troubleshooting steps and solutions outlined in this article, you should be able to fix the “kex_exchange_identification: connection closed by remote host” error and successfully connect to the remote server via SSH.

Always double-check your login credentials and network connection and contact the server administrator or network administrator for assistance if needed.

Frequently Asked Questions

What should I do if I’m still experiencing the error after trying the solutions in the article?

If you’re still experiencing the error after trying the solutions in the article, you should contact the server administrator or network administrator for assistance. They may be able to provide additional troubleshooting steps or information that can help resolve the issue.

Why is my firewall blocking the connection?

A firewall can block the connection for several reasons, such as security reasons, preventing unauthorized access to the server, or due to a configuration error. It is important to check your firewall settings and ensure it is not blocking the connection.

How can I check for existing ssh-keys?

You can check for existing ssh-keys by trying to connect to the server with the ssh -v option. It will give you more details about the connection process and whether the remote server accepts your key.

You can also check on the remote server in the authorized_keys file to see if your key is still valid and authorized.