who_you_are

Hum, then I am missing something because portzilla is just a reverse proxy by the look of it

This mean:

• you need to use http (games and ftp don't)

Or

• you have multiple IPs (one per sub domain if I want to go with the examples from portzilla).

I assumed OP was in IPV4 and only has one IP.

Just to be sure from my other assumptions (kinda ELI5)

• DNS doesn't exist on the transport layer. It is converted to an IP and your computer just try to connect to that IP. So whatever DNS you use, if they point to the same IP you have no way to distinguish from what "DNS" they want to go.

This is how networking works. Only with IP, no DNS.

• some applications (http), added support for DNS. When the user type a DNS, even if your computer still use IP to reach the server, the browser will introduce itself by telling the server the DNS it tried to reach.

tons of subdomains instead of ports

Just to be clear for OP, that applies only for protocols that "support DNS" as in, they send the DNS in the protocol.

The one I have in mind: http(s) and emails.

Games, FTP and most of the protocols don't.

VLAN (assuming the camera is plugged to your LAN infrastructure) + a firewall (to block the MAC + every kind of traffic except the one expected from the camera; down to the IP + PORT + Protocol)