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Re: possible ssh problem


On 8/29/25 4:31 PM, Greg Wooledge wrote:
On Fri, Aug 29, 2025 at 16:01:53 -0700, Paul Scott wrote:

On 8/29/25 3:40 PM, Andy Smith wrote:
1) Your dyndns.org entry is not pointing to the correct IP address.

ping and looking at my account on dyndns.org, the IP is correct.

Let's say your dyndns name is paul, so I can write meaningful sentences.

Do you mean you simply ran 'ping paul.dyndns.org' and then looked at
something on the dyndns.org web site (after logging in as paul), and
they happened to agree with each other?

Well of course they did.  This is meaningless.

Doesn't this at least tell me that ddclient on the desktop is working?


What you need to compare are the IP in dyndns against your *actual IP*
address.

You can determine your actual IP address by doing something like

    curl http://wooledge.org/myip.cgi

There are many other sites that offer the same service.

Ok. Since the desktop is not physically available to me right now, I wiil do this sometime tomorrow.

(I thought I had done this a few days ago with the correct result but I will check again tomorrow.)




2) Your ISP is blocking incoming connections, either on port 22 or on
   all ports, before it hits your router/server.

I'm not sure how to determine that.

Not easily done, admittedly.  It's a process of elimination thing.  When
you've verified that EVERY single thing is in place and working, then
by process of elimination, if the incoming connections still aren't
working from multiple client systems, you might conclude that your ISP
has set up a firewall.


3) Your router is blocking incoming connections, either on port 22 or
   on all ports.

4) You've forgotten to configure your router to forward incoming port 22
   to your internal host.

5) You've configured your router to forward incoming port 22, but to the
   wrong internal IP address.

I haven't knowingly changed anything on my router.

Instead of saying "I don't know", go *find out* the answers.  These are
prompts for you.  It's not a closed-book quiz.
I will not take that as an insult since I'm not sure what you mean by 
It's not a closed-book quiz.

Look at #4 for example.  Instead of shrugging and saying "I don't know",
go look at your router's configuration.
Again, If knew enough, I wouldn't be asking for help.
 Log into it, and look at the
web interface it presents.  Find the place where port forwarding is
set up.  You MUST have set this up at some point, if it ever worked at
all.  This is not a thing that will ever work out of the box.

I probably did this 10 years ago.

port forwarding is enabled.

ssh is port 22 with a local IP that looks correct but I will have to check tomorrow/

The protocol is TCP 

So, find where the port forwarding is configured, and LOOK at it.  See
if it's correct.  The internal IP address and port number that the ssh
connections are being forwarded to must match your Debian system's LAN
IP address and your sshd's listening port number.
Thank you for the help. If I had known that, I probably wouldn't be asking these questions.

You can get your Debian system's IP address using

    ip -brief addr

or a huge variety of similar/variant commands.

You can get your sshd's listening port using

    grep Port /etc/ssh/sshd_config

or by reading the whole file to see the lines in context.  Other ways
to accomplish a similar goal would include

    sudo ss -ntlp | grep sshd
    sudo lsof -i | grep sshd

and so on.  Those will look for an actual sshd process and see what
it's listening to.  The /etc/ssh/sshd_config file will show what the
sshd process *should* be listening to, if it's running, but won't
tell you that it's actually running.

I can only do the above in the next few days when I have physical access to the desktop.

Thank you for all your help,

Paul



    

  







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