A Practical Guide to SSH Tunnels: Local and Remote Port Forwarding
labs.iximiuz.com79 points by signa11 4 days ago
79 points by signa11 4 days ago
If you have many different remote devices behind NATs or firewalls, a cool trick to access them all via EC2 server (or such) is to setup Remote Forwarding via UNIX socket on the server side, to devices' port 22. Preferably, UNIX socket filenames should start with a common prefix, so an SSH config can be written that will use ssh+socat in a ProxyCommand to establish the connection.
It's amazing how lightweight this method actually is. I have managed to connect hundreds of devices using a single EC2 nano instance.
I never pass up an opportunity to recommend the Cyber Plumber's Handbook: https://github.com/opsdisk/the_cyber_plumbers_handbook
Goes over similar content as TFA, in perhaps a little more depth. Indispensable sysadmin knowledge.
I'll mention it here, because I learned about it here.
"~C" will drop you into the SSH command line, allowing you to, among other things, effect port forwarding
-L8080:localhost:443
But for some reason this has been disabled by default in more recent ssh configurations... to ensure its available
-o EnableEscapeCommandline=yes
EnableEscapeCommandline yes
Important to note that `~` SSH commands work only right after you press Enter - it doesn’t trigger everywhere you press `~`.
Also EnableEscapeCommandline fortunately only affects `~C` - the all-important `~.` to kill a hung SSH session still works with it disabled.
Learning how SSH port forwarding is great as a pseudo-vpn for everything from GUI-client database access to (in physical infra) access to web-admin tools for appliances.
The socks proxy support can also deal with bad web filtering and privacy issues on public wifi networks (though nowadays if you're ssh'ing to a cloud IP, you'll get lots of "bot" restrictions).
The article mentions bastions, but no jumphosting?
ssh -J user1@bastion1,user2@bastion2 targetuser@targethost
It is surprising how many times I see this content (this version might be marked “Published: Jun 19, 2026” but I've definitely seen those exact diagrams before, starting at least a few years ago, and the same content around them in many tutorials before that) without it being updated to mention jump-hosts.
Support was added to OpenSSH about a decade ago? Even on a low moving Linux distro like Debian/LTS everyone should have support by now.
It’s amazing what you can learn by reading the manual.
It is, because manuals are often not the best way to learn things. Most software manuals are reference manuals. SSH man page isn't too bad. I learned most of my SSH knowledge from it, but I'm not sure it's the best way to do it.
For me, the best way to learn a tool is for a quick example or two showing its utility, then practicing with those, reading the man as needed on specific flags. Google or bot ”how do x" ? Repeat : done
Some pages have a nice up-front synopsis of flags, others put them in a wall of text. Browsing the former can supplant Google, /\b-x while paging is helpful for the latter.
There's a asymmetry here that "-R" works both for reverse static and dynamic (using SOCKS protocol) forwarding, but "-D" is required for dynamic forwarding which "-L" cannot do.
Why is that?
Or you could just install something like Tailscale and never have to think about it again.
When I see one of these with obvious AI tells at the top (sentences lacking a subject or verb), I ask myself:
Can’t I just open up a harness and prompt “Teach me how to do X?”
I do this all the time, I have a skill/gem with instructions on how I want to receive info, how to format and so on. Really helps to go fast to get the point.
I personally do this, ask claude code to teach me about concepts I don't know about when it codes something, and only then I accept what it suggests to me
As a sysadmin, one of your biggest ROI is learning the ins and outs of SSH.
Very refreshing to see a utilitarian series such as this. Disappointing that the latest ai drama gets 20x more discussion and visibility on this site