SSH tunneling (also known as SSH port forwarding) is powerful technique that allows system administrators to create secure encrypted connections between servers, bypass firewalls, and access services securely across networks. Its also known as SSH magics! Whether you’re trying to securely access internal services, create SOCKS proxies, or establish reverse tunnels to overcome network restrictions, SSH tunnels provide flexible solutions for modern networking challenges. This comprehensive guide explores essential SSH tunneling commands that every system administrator should know, complete with practical examples and use cases to enhance your network security toolkit. So let’s get on with some SSH magics, shall we?

It's 2024! Please avoid writing SSH commands like that.

Instead, configure your ~/.ssh/config with LocalForward, RemoteForward, and ProxyJump. This can save you a significant amount of time, especially when using ssh, scp, or rsync to transfer data from a remote server that requires multiple intermediate SSH connections.

Ever need to work on a remote computer which is behind a typical firewall. Well if there is no inbound connectivity, you can play a bit of leap frog using ssh in order to gain access to that server. Here’s a quick example.
For this example we’ll assume you are sitting at Host A and would like to have access to Internal Host C. Both firewalls are assumed to allow ssh traffic out.
Our goal here is to have the Internal Host C machine start an ssh session to External Host B (which is on the internet).
SSH -R 2200:localhost:22 User@ExternalHostB
This will start an ssh session from Internal Host C to External Host B and ask the ssh daemon to forward all traffic on External Host B’s port 2200 back to Internal Host C’s port 22 over the established ssh session.
Now If I were on External Host B, to get a shell on Internal Host C all I’d have to do is:
SSH -p 2200 User@localhost
Now the USER in the above statement would have to be a valid user on Internal Host C, not External Host B.
To connect from Host A to Internal Host C you can do several things. The easiest is to leap frog.
SSH USER@ExternalHostB
Then
SSH -p 2200 USER@localhost
The first session opens a shell on External Host B. The second opens a shell on Internal Host C by connecting to the reverse shell we started in the first command.
This has been a simple reverse shell ssh post. Stay tuned for more port forwarding fun.

SH tunneling and port forwarding can be used to forward TCP traffic over a secure SSH connection from the SSH client to the SSH server, or vice versa. TCP ports or UNIX sockets can be used, but in this post I’ll focus on TCP ports only.

I won’t go into details, but the following post should show enough examples and options to find use in your day-to-day work.