server 2012 ssh network error connection refused

When attempting to establish a Secure Shell (SSH) connection to a server running Windows Server 2012, encountering a “Network error: Connection refused” message can be frustrating. This error indicates that the client’s attempt to connect to the server’s SSH port was rejected. There are several reasons why this might occur, ranging from service issues to network configurations.

Potential Causes of Connection Refusal

Before diving into troubleshooting, it’s essential to understand the potential causes behind the connection refusal:

SSH Service Not Running: The SSH server might not be running on the target machine.
Firewall Restrictions: Firewall settings could be blocking the SSH port (default is 22).
Incorrect IP Address or Port: The client may be trying to connect to the wrong IP address or port.
Max Startups Exceeded: The maximum number of concurrent connections to the SSH server has been exceeded.
SSH Configuration Issues: Misconfiguration in the SSH server settings can prevent successful connections.

Verifying SSH Service Status and Configuration

The first step in resolving the “Connection refused” error is to ensure that the SSH service is up and running on the server. Here’s how you can verify and configure the SSH service on Windows Server 2012:


# Check if the SSH service is running
Get-Service -Name sshd

# If the service is stopped, start it using
Start-Service -Name sshd

# To set the SSH service to start automatically with the system
Set-Service -Name sshd -StartupType 'Automatic'

If the SSH service is not installed, you will need to install it via the Server Manager or PowerShell.

Checking Firewall Settings

After confirming that the SSH service is active, the next step is to check the firewall settings. Ensure that the firewall allows traffic on the SSH port (usually port 22). You can adjust the firewall settings using the following PowerShell commands:


# To create a new rule allowing SSH traffic
New-NetFirewallRule -Name sshd -DisplayName 'SSH' -Enabled True -Direction Inbound -Protocol TCP -Action Allow -LocalPort 22

Validating Client-Side Configurations

On the client side, make sure you’re connecting to the correct IP address and port. Use tools like ping or telnet to test connectivity to the server’s IP address on the SSH port.


# Test connectivity to the server's SSH port
telnet SERVER_IP 22

If telnet is unable to connect, it suggests a network issue or incorrect IP/port information.

Investigating Max Startups and Concurrent Connections

If the server has reached its limit for concurrent SSH connections, new attempts will be refused. Check the sshd_config file for the MaxStartups directive and consider increasing the limit if necessary.

Resolving SSH Configuration Issues

Misconfigurations in the SSH daemon settings can also lead to connection refusals. Review the sshd_config file for any incorrect settings that might be causing the issue. Pay special attention to directives such as ListenAddress, which specifies the IP addresses sshd should listen on.

Troubleshooting Steps for Resolving Connection Issues

Here are some systematic troubleshooting steps to resolve the “Connection refused” error:

Restart the SSH service on the server.
Verify that the SSH server is listening on the expected IP address and port.
Check for any recent changes in network policies or firewall rules.
Ensure that the server’s host keys have not changed unexpectedly.
Review the SSH server logs for any error messages or clues.

Case Studies and Real-World Examples

To illustrate common scenarios where users face the “Connection refused” error, let’s look at a couple of case studies:

Case Study 1: Firewall Misconfiguration

In this scenario, an administrator had recently applied new firewall rules to the server, inadvertently blocking the default SSH port. By reviewing the firewall logs and configurations, they identified and corrected the oversight, restoring SSH access.

Case Study 2: SSH Service Disabled

A company’s policy required disabling all unnecessary services on their servers. During routine maintenance, the SSH service was mistakenly disabled, leading to connection refusals. Once the error was discovered, the service was re-enabled, solving the problem.

FAQ Section

What does “Connection refused” mean when trying to SSH into a server?

It means the server is actively rejecting the connection request, often due to service issues, firewall blocks, or misconfigurations.

How do I check if the SSH service is running on Windows Server 2012?

Use the PowerShell command

Get-Service -Name sshd

to check the status of the SSH service.

Can firewalls cause an SSH “Connection refused” error?

Yes, if a firewall is configured to block incoming connections on the SSH port, it will result in a “Connection refused” error.

Is it possible that too many SSH connections can cause this error?

Yes, if the server reaches its maximum allowed concurrent SSH connections, additional connection attempts will be refused.

References

For further reading and external resources, consider the following references:

Microsoft TechNet: Configure Windows Firewall for Remote Debugging – technet.microsoft.com
OpenSSH: The OpenSSH project provides a free version of the SSH connectivity tools – openssh.com
Internet Engineering Task Force (IETF): RFC 4253 – The Secure Shell (SSH) Transport Layer Protocol – tools.ietf.org/html/rfc4253