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How to Fix ssh_exchange_identification Error on Windows 11: Complete Troubleshooting Steps

Encountering the ssh_exchange_identification error on Windows 11 can be frustrating, especially when you’re trying to connect to a remote server via SSH. This error usually indicates a problem during the initial handshake between your client and the server.

Fortunately, fixing this error involves a few straightforward troubleshooting steps. This guide will walk you through the process in the simplest way possible, even if you’re new to SSH or Windows.

By following these steps, you will better understand what causes the error and how to resolve it effectively. Let’s get started and restore your SSH connection.

Remember, patience and careful checking are key to solving connection issues.

Quick Note: Prerequisites and Initial Checks

Before diving into the troubleshooting steps, ensure the following:

  • You have administrative access to your Windows 11 machine.
  • The remote server you are trying to connect to is powered on and reachable over the network.
  • Your SSH client is installed and updated. Windows 11 comes with OpenSSH built-in, but verify by running ssh -V in Command Prompt or PowerShell.
  • You have the correct IP address or hostname and port number for the SSH connection.
  • No firewall or antivirus on your machine or network is blocking SSH connections.

Step 1: Check the SSH Server Status

The ssh_exchange_identification error often appears if the SSH server is not running or is overloaded. To confirm the server status:

  • Try to ping the server by opening Command Prompt or PowerShell and running:
    ping [server_ip_or_hostname]
  • If ping fails, it means the server is unreachable. Check your network connection or contact your server administrator.
  • If ping succeeds, the server is reachable, so the problem may lie with the SSH service itself.
  • If you have access to the server, log in locally or via another method and restart the SSH service using the command:
    sudo systemctl restart sshd (Linux) or the equivalent on your server OS.

Restarting the SSH service can clear temporary issues causing the handshake failure.

Step 2: Verify SSH Configuration Files

Sometimes, misconfigurations in the SSH server’s files can cause connection refusal. On the server side:

  • Check the /etc/ssh/sshd_config file for any mistakes or unusual settings.
  • Look for directives like DenyUsers, DenyGroups, AllowUsers, or AllowGroups that might block your user.
  • Ensure the server is listening on the correct port, usually port 22, by verifying the Port directive.
  • After changes, always restart the SSH service to apply them.

Incorrect configurations can prevent proper SSH connections and cause the ssh_exchange_identification error.

Step 3: Check for TCP Wrappers and Host Access Restrictions

Many Linux servers use TCP wrappers to control access to services. Files like /etc/hosts.allow and /etc/hosts.deny can block SSH connections.

  • On the server, open /etc/hosts.deny and see if SSH (sshd) is denied. For example, a line like sshd: ALL blocks all SSH connections.
  • If so, remove or comment out such lines.
  • In /etc/hosts.allow, ensure your client’s IP address or range is allowed to connect.
  • These files act as an additional layer of security and can cause the handshake to fail if misconfigured.

Step 4: Examine Firewall and Security Software

Firewalls on either your Windows 11 machine or the server can block SSH connections, resulting in this error.

  • On Windows 11, open Windows Defender Firewall and check if outbound SSH connections (port 22) are allowed.
  • Temporarily disable any third-party antivirus or firewall software to test if they are causing the issue.
  • On the server, verify that the firewall (such as ufw or firewalld) allows incoming SSH connections:
sudo ufw status
sudo firewall-cmd --list-all

If SSH is blocked, add a rule to allow it:

sudo ufw allow ssh
sudo firewall-cmd --add-service=ssh --permanent
sudo firewall-cmd --reload

Firewall rules are essential for network security but must be configured correctly to allow legitimate SSH traffic.

Step 5: Review SSH Logs for Detailed Errors

Logs provide valuable insights into why the SSH handshake fails. On the server, you can check SSH logs by running:

sudo tail -f /var/log/auth.log

or on some systems:

sudo journalctl -u sshd

Look for error messages related to your connection attempt. Common issues include too many connections, authentication failures, or IP bans.

Identifying specific log entries helps target the problem more accurately.

Step 6: Check for MaxStartups Limit

SSH servers limit the number of simultaneous unauthenticated connections via the MaxStartups setting to prevent abuse. If this limit is exceeded, new connections may be refused and cause the error.

  • In the /etc/ssh/sshd_config file, look for the MaxStartups directive.
  • The default is often 10:30:100, which means it allows 10 unauthenticated connections, then starts dropping some up to 100.
  • If you are running multiple SSH sessions or automated scripts, increase this value to a higher number.
  • After updating, restart the SSH service.

Step 7: Try Connecting with Verbose SSH Output

When connecting from Windows 11, run SSH with verbose mode to get more information about the failure:

ssh -vvv user@server_ip

This command outputs detailed debug information during the connection process. Review the output for clues such as timeout points or authentication issues.

Verbose mode helps you understand exactly where the handshake is failing.

Alternative Methods and Advanced Options

If standard fixes don’t work, consider these alternatives:

  • Use a different SSH client: Try tools like PuTTY or MobaXterm on Windows 11 to rule out client-side problems.
  • Check TCP Wrapper alternatives: Some servers use fail2ban or other security daemons that may block your IP after repeated failed attempts. Review and whitelist your IP if necessary.
  • Test SSH on a different network: Sometimes corporate or public networks block SSH traffic. Try connecting from a home network or mobile hotspot.
  • Check Windows Subsystem for Linux (WSL): If you use WSL on Windows 11, ensure its networking is configured correctly and does not interfere with SSH connections.

Frequently Asked Questions (FAQs)

What does ssh_exchange_identification mean?

This error indicates that the SSH client and server failed to complete the initial handshake. It usually means the server refused the connection or dropped it before authentication.

Is this error caused by my Windows 11 machine or the server?

It can be either, but most often the issue lies on the server side, such as SSH service problems, firewall rules, or security restrictions.

Can antivirus on Windows 11 cause this error?

Yes, some antivirus or firewall software may block outgoing SSH connections. Temporarily disabling them can help identify if they are the cause.

How do I know if my IP is blocked by the server?

Check the server’s /etc/hosts.deny file, firewall rules, and fail2ban logs. You can also try connecting from a different IP to test.

Is it safe to increase MaxStartups on the server?

Yes, but only moderately. Increasing it too much may expose the server to denial-of-service attacks. Adjust carefully based on usage.

When Nothing Works

If you have tried all the above steps and still face the ssh_exchange_identification error, consider the following:

  • Contact your server administrator or hosting provider for assistance. They may have system-level restrictions or issues.
  • Review official OpenSSH documentation and forums for your server’s operating system for known bugs or patches.
  • Reboot the server if possible, as some SSH issues clear after a restart.
  • Use official Microsoft support if the problem is suspected to be on the Windows 11 client side.

Here are some useful official resources:

Conclusion

The ssh_exchange_identification error on Windows 11 can seem complicated, but by methodically checking your server status, configurations, firewall settings, and logs, you can usually resolve it quickly.

Start with basic network checks and move toward more advanced server-side configurations. Using verbose SSH output and alternative clients can provide additional clues.

Remember to verify both client and server sides and consider security software that might interfere. If all else fails, reaching out to your server’s support team is a practical next step.

With patience and these troubleshooting steps, you’ll be able to restore your SSH connection and continue your work smoothly.

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