What is the default port for SSH?

The Default Port for SSH

The default port for the Secure Shell (SSH) protocol is port 22. SSH is a widely used protocol that allows secure remote access to computers and servers over a network connection.

Why Port 22?

The choice of port 22 as the default for SSH is historical. When SSH was first developed in the 1990s, port 22 was selected as the standard port for the protocol. This was because port 22 was not commonly used by other network services, making it a suitable choice for SSH.

The use of a well-known and standardized port number helps ensure compatibility and ease of use. By using port 22, SSH clients and servers can automatically connect to the appropriate port without the need for additional configuration.

graph LR A[Client] -- SSH Connection --> B[Server] B -- Listens on Port 22 --> A

Changing the Default Port

While port 22 is the standard and most commonly used port for SSH, it is possible to configure the SSH server to listen on a different port. This can be done for various reasons, such as:

Security: Changing the default port can help to reduce the risk of unauthorized access attempts, as attackers often target the well-known port 22.
Firewall Configuration: Some organizations may have firewall rules that block access to port 22, requiring the use of a different port for SSH connections.
Multiple SSH Servers: If you have multiple SSH servers on the same network, using different ports can help to distinguish between them and simplify management.

To change the default SSH port, you would need to modify the SSH server configuration file, typically located at /etc/ssh/sshd_config. For example, to set the SSH server to listen on port 2222 instead of the default 22, you would add the following line to the configuration file:

Port 2222

After making the change, you would need to restart the SSH server for the new port setting to take effect.

graph LR A[Client] -- SSH Connection --> B[Server] B -- Listens on Port 2222 --> A

In summary, the default port for SSH is 22, but it can be changed to a different port if needed for security, firewall configuration, or other reasons. Knowing the default port and how to modify it is an important part of understanding and working with SSH in a Linux environment.