All the notice means is that people on the internet can access your DNS server to resolve queries.
The reason this is happening is because you have configured the server as the DMZ. This is a very bad idea.
Port forward only the neccessary ports required for external access. i.e.,perhaps 443 for SSTP VPN and perhaps 3389 for remote administrative access, and whatever else you require. You should not forward all the ports to the server (which is what putting it as the DMZ does), this is exposing the server to significant hacking attempts unneccessarily. At the moment any connection attempt to your static IP is being forwarded to your server, that includes file and print sharing, and god knows what else.
It is better practice on the DNS manager tab to select only the valid interface. This is because if IPv6 comes available the server will automatically start responding to queries on it's IPV6 interface. You do not want this to happen automatically. So just select the interface you want it to start responding on.
Leave the DNS forwarder as it is, this is all fine. The "router.asus.com" is just your router trying to give itsself a friendly name.
ZeN Fibre Unlimited 2
Edited by Pipexer (Sun 13-Mar-16 17:08:04)