Generic:

$ ssh -N -f -L <local_port>:<end_server>:<end_port> user@ssh_intermediary_server

NOTE: if using auth. w/keys and no passwd, the last part (user@…) is not needed

Example:

$ ssh -f -N -L 8025:smtp.comcast.net:25 my_home_machine -L 8110:mail.comcast.net:110 my_home_machine

allows me to use the email client on a laptop, pointing to localhost:8025 for SMTP services, and localhost:8110 for POP3 services associated with my Comcast account, w/out traversing “foreign” networks with clear text credentials.

If moving between places, I would need tostop and restart the process. This could be as simple as:

$ ps aux |grep ssh |grep -v grep |awk ‘{print $2}’ |xargs kill -9