If you still don’t have an open NAT even though all the required ports have been forwarded, you may need to use DMZ on your ISP Modem or on your DumaOS powered router.
First check if the Modem/Router has Modem or Bridge Mode as this is preferable over DMZ mode. To put your DumaOS powered router into the DMZ of your ISP Modem, first navigate to System Information. On the Internet Status panel, highlight the number next to ‘WAN IP Address’ and copy it. Next, head to the interface of your ISP Modem and go to the Security / Firewall Settings. You should see a box labelled ‘DMZ IP Address’. Paste the WAN IP Address into this box and make sure DMZ is enabled. You have now successfully put your router into DMZ mode.
If this step does not work you can put your games console into the DMZ of your router. (This option is not available on the Netduma R1.) To do this, first find the IP address of your console. You can check this on the Device Manager R-App, or alternatively you can find this in Network Settings on your console. Next, navigate to Settings > WAN Setup on your DumaOS powered router and type the IP address of your console into the DMZ text box, then click apply at the bottom of the page. You have now successfully put your console into the DMZ of your router.