SSH Tunneling

SSH tunneling simply redirects all traffic from a remote port of a remote host to your local box on a local port:

Example:

ssh -f user@personal-server.com -L 2000:personal-server.com:25 -N

The -f tells ssh to go into the background just before it executes the command. This is followed by the username and server you are logging into. The -L 2000:personal-server.com:25 is in the form of -L local-port:host:remote-port. Finally the -N instructs OpenSSH to not execute a command on the remote system.

http://www.revsys.com/writings/quicktips/ssh-tunnel.html