![]() username is the username to log into the jump host.ssh is the command we are using for our ssh tunnel.Access a network device/server that is only accessible via a jumphost You specify a local port for SSH to listen on, such as 4001, and all connections destined for port 4001 will be tunneled via SSH to a specified remote port, such as 22. What is an SSH Tunnel?Īn ssh tunnel aka ssh port forwarding, allows an encrypted tunnel to be established over an untrusted network between an SSH Client and SSH server. However, as long as you have access to the jumphost, you may be able to use an ssh tunnel to mimic being directly connected to a network with access to the otherwise inaccessible hosts. That’s all I wanted to show you! If you enjoyed this lesson, please leave a comment.Do you have a network device or server that can only be reached behind a jumphost? This is not an uncommon scenario, as security best practice often requires such. We will connect our local port 5000 to the remote web server (192.168.2.1 port 80) and connect to SSH server 1.2.3.4. ![]() ![]() The above line is similar to the configuration I showed you in Putty. ![]() If you are using Linux or MAC, you don’t have to use putty, but you can use the command line, which is a lot easier: sudo ssh -L 5000:192.168.2.1:80 1.2.3.4 Everything it sends through this SSH tunnel is safe because it’s encrypted. The cool thing about SSH is that you only need to open one single port, and by tunneling traffic like this, you can reach any device behind the SSH server. As you can see, it connects to the webserver! Whenever you connect to localhost port 5000, it will be forwarded to IP address 192.168.2.1 port 80. I’ll type in “localhost,” which refers to my local computer, and port number 5000, the source port I chose for the port forwarding in putty. Let’s open a web browser and connect to the webserver: You will see the normal SSH login screen, but our port will be forwarded in the background. Now hit the “Open” button and type in the username and password that you normally use. It will show you which ports will be forwarded. Click on the “Add” button, and it will look like this: You can pick any source port that you like. I want to reach the web server, so the destination will be IP address 192.168.2.1 and port 80. Finally, select “Tunnels” to configure SSH port forwarding. Take a look at the screenshot below:Ĭlick on “connection” to expand it and select “SSH”. We can connect to the router using SSH, but perhaps you didn’t know it’s also possible to reach the webserver through the SSH tunnel! Let me show you how to do this with putty:įirst, I will type in the IP address of the SSH server, but before we click on “open”, we’ll configure SSH tunneling. On the right side, there’s also a web server with IP address 192.168.2.1. In my picture, this is a router, but you can run an SSH server on many devices, including Windows, Linux, Mac, routers, and storage devices from Synology or Qnap. On the right side, we have an SSH server with public IP address 1.2.3.4. If you are using Linux or a Mac, you can use SSH from the command line. The most popular SSH client for Windows is putty, and you can download it for free. This computer is on our LAN and has IP address 192.168.1.1. Let me show you a picture to explain this:Ībove, you see an SSH client on the left side. ![]() Besides being able to reach hosts behind the SSH server, our traffic is also secure because SSH will encrypt it. It works the same way as a VPN as you can reach all hosts behind the SSH server. Besides using SSH to connect to (Linux) servers or network equipment, you can also use it to tunnel traffic. ![]()
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