Model :

Hardware Version :

Firmware Version :

ISP :

I am using a TL MR3420 router with a 3G Huawei USB dongle to connect to the internet a network camera

I obtained from the provider a public IP address so than I can ping and find it on the internet.
I forwarded the port assigned to the fixed IP address camera and even assigned a DMZ status to the camera

However checking the port by:
https://www.yougetsignal.com/tools/open-ports/
I always find it closed so that eventually connecting by a DDNS server doesn't work

I read on a similar thread:
http://forum.tp-link.com/showthread.php?84961-Port-Forwarding&highlight=port+forwarding+dongle
that it's not necessary to forward a port when using a USB dongle
Now how would the traffic directed to the camera be routed to its IP address?

Any suggestion to solve the issue?
thanks