Tag Archives: tunnel

Remote port forwarding via SSH

Imagine that you want to access a specific port on a remote server from your local machine. Basically, a “remote port forwarding”.

This remote server is not accessible directly from internet. It is NAT’d behind firewall.
To access the remote server you need to connect firstly to a remote bastion server (accessible from internet) and from there, you will be able to access the server.
Your current machine is also within restricted network and unable to ssh out. You can ssh into a local bastion server only. From this local bastion you can ssh out.

As long as you have access to the 2 bastions servers, you will be able to run the following script.

The script points/links a local_port on your local machine to the ssh port of the remote bastion, via your local bastion.
After that, it will connect the remote port or the remote server to a new_local_port, ssh’ing via local_port.

Example below shows a way to have the VNC port 5900 available locally on port 5910.
I’m using port 8888 as local port.
Local Bastion ssh port is 8022.
Remote Bastion ssh port is 9022.

Example:

 

And here a full script:

 

SSH tunnel from A to B via jumpbox

Here a basic script that you can use if you want to connect from your local box, via a middle linux machine, to a third host.
It will also allow you to use FoxyProxy on your browser and browse the internal network of the destination box.

BOX_A <==== MIDDLE_BOX ====> BOX_B

The goal is having access from BOX_A to BOX_B via MIDDLE_BOX

MIDDLE_BOX is the only one that can talk withBOX_A and BOX_B