I have successfully set up DynDns for my Redhat machine through D-Link router, then DSL. Then I have a new machine installed Debian that I am trying to connect to DynDns. Don't ask me why I have both Redhat and Debian :-((

As an example, let me assume that I use the following domain names:

redhat.dyndns.org for the redhat machine.

debian.dyndns.org for the Debian machine.

Don't ask me why I set up two machines either :-(( Anyway, the ddclient.conf looks as follows.

pid=/var/run/ddclient.pid
use=web
login=MY_DYNDNS_NAME
password=MY_DYNDNS_PASSWORD
server=members.dyndns.org, \
protocol=dyndns2 \
debian.dyndns.org

I saw the IP address is updated. Unfortunately, when I do

ssh debian.dyndns.org

it always go to redhat machine!!!!

When I shut down the redhat machine. The update still happens but the ssh cannot find the machine. I suspect that is something related to the router. I don't remember I did anything :-(((

Any shark knows the solution?

So you have two machines on the same public IP address. You can't forward SSH port to both of them at the same time. Your router is apparently set up to forward port 22 to your RedHat machine.

So what you should do is set a different SSH port on the Debian machine. Then tell your router to forward that port to the Debian machine. And then use that port whenever you need to SSH to the Debian machine.