ssh(1) -L
OpenSSH SSH client (remote login program)
-L [bind_address:]port:host:hostport
        Specifies that the given port on the local (client) host is to be forwarded to the given host and
        port on the remote side.  This works by allocating a socket to listen to port on the local side,
        optionally bound to the specified bind_address.  Whenever a connection is made to this port, the
        connection is forwarded over the secure channel, and a connection is made to host port hostport
        from the remote machine.  Port forwardings can also be specified in the configuration file.  IPv6
        addresses can be specified by enclosing the address in square brackets.  Only the superuser can
        forward privileged ports.  By default, the local port is bound in accordance with the GatewayPorts
        setting.  However, an explicit bind_address may be used to bind the connection to a specific
        address.  The bind_address of “localhost” indicates that the listening port be bound for local use
        only, while an empty address or ‘*’ indicates that the port should be available from all
source manpages: ssh