The port is already open and being used by another service. The warning is in regard to remote access, which is what they are used for, and is meant to make rookies think twice before enabling any other services to use those ports.
I am unable to make the 443 to work but other ports i.e., 21, 80, 25 are working fine and ISP insists that they do not block port 443.
My web server firewall is OFF and web server is listening to 443. I have even connected the web server directly to ISP and could not make it work.
So, when I login to my router I see the "WARNING: Ports 22 and 443 are reserved by the service provider, use with caution! If needed, use these port numbers behind the router and arbitrary port numbers on the outside of the router."
The warning notice is confusing me as it says 22/443 are reserved by ISP and use them with caution!? If they are reserved how can I use them?
Is this wrong sentence or am I not able to understand it technically?