How to setup SSH tunneling on Linux

SSH tunneling commonly known as SSH port forwarding is a technique of routing local network traffic over through encrypted SSH on remote hosts. Routing network traffic via SSH tunnels ensure high level of data encryption and security, especially for unencrypted network protocols such as FTP. This is very useful especially when connected to unsecured networks.

This tutorial will explain how to set up an SSH tunnel and securely route your traffic via secure tunnels. We will discuss all three methods of SSH port forwarding:

1. Local Port forwarding
2. Remote Port Forwarding
3. Dynamic Port forwarding

Perquisites

For this tutorial, you are going to need:

1. A local machine
2. A remote host such as a VPS

Local Port Forwarding

This type of port forwarding allows you to forward a port on the local machine to a specific port on a remote machine which is then forwarded to the destination address.

Local port forwarding allows the local machine to listen on a given port and tunnel any traffic to the specific port to the port specified on the remote server. Once the remote server receives the traffic, it is forwarded to the set destination address.

To create a local port forward, we use the -L flag for the SSH command:

The general syntax is:

If you do not specify LOCAL_IP, the local SSH client will automatically bind to localhost. You also need to specify ports larger than 1024 as they are not restricted to root users only.

Assume you have a service running on the machine my.service on port 5000 and can only be accessed on machine access.machine. If you want to connect to the service from your local machine, you need to forward your connection as:

Once you execute the command, you will need to provide the SSH password for the specified user. For ease of use, you can set a password-less login using SSH keys.

You can now access the service from your local machine using the port specified (5555) where the access.machine acts as intermediate.