I've been using Shields Up to check which ports are visible from the Internet.
With my NAT router set up as normal, all ports show as "stealthed" in Shields Up i.e. a probe to the port gives no response. This is viewed as a good thing.
When I DMZ to my Pi (running a VPN server as a test) I can see all the ports as "closed" apart from the VPN port. As I understand it the Pi is sending a negative response to a request to open the port. This tells the far end that there is a device there managing the ports, which is an invitation to try again and expand the range of ports probed.
I would like to tell the Pi to ignore all connection requests and stealth the ports.
Google is not currently my friend. Does anyone know how to do this?
Cheers
Dave R