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The Secure Shell protocol authenticates and encrypts network connections. Find out how it's used to build tunnels while crossing private networks and even firewalls

The Secure Shell protocol defines a mechanism for securely connecting to a remote host. Originally, SSH was intended to replace Telnet, the original internet application for running remote login sessions. But SSH has become much more than a tool for terminal emulation, in large part because it provides the means to securely route network traffic through ports and host systems defined by the user. These connections are called tunnels because they provide a connection through which secure network data can be transmitted over an unsecured network.

An SSH tunnel is a secure connection between an SSH client and an SSH server. Network traffic from the local machine is routed from an arbitrary specified port on the localhost through the SSH connection to a specified port on the remote machine.