in IT linux ~ read.

Remote and Local SSH tunneling easily

Every flipping time I am trying to use SSH tunneling I am confused what part of the command is for local and which for remote host. Here is what I have finally realized (I know it's stupid, but it helped me).

Local with -L switch

When you run something on the remote server and you need to tunnel from your client to the server, you use on the client this command:

ssh -N -f -L your_wished_ip:your_wished_port:ip_on_the_server_where_the_service_is_running:port_on_the_server_where_the_service_is_running username_on_the_server@address_of_the_server  

so e.g. I am running Jupyter notebook on the server on the address localhost and port 3456 and want to tunnel there from my computer on and port 9843. Then the command is:

ssh -N -f -L username@ip.address.of.server  

Remote with -R switch

It's exactly opposite as it is with the -L switch. This is a bit confusing, but make sense. As a mnemonic technique, the switch tells you who is specified first. So let say that I want to share my IPython notebook running on localhost:8888 on my client with someone else through my server. I would do this:

ssh -N -R localhost:8889:localhost:8888 serverSSHProfile  

this will allow someone else to tunnel to my webserver using the -L switch as this:

ssh -N -f -L localhost:8881:localhost:8889 username@ip.address.of.server  

and she could open web browser on localhost:8881 to see my IPython notebook.

One more thing

To make it even messier, you should be able to open that port to the whole port by doing this:

ssh -N -R :8889:localhost:8888 serverSSHProfile  

anyone who now hits your.server.address:8889 should be able to see your IPython notebook, which makes me scared. To be fair, I wasn't able to get through for unknown reason (page just loads infinitely long).