Port Forwarding issues

Hello everybody, I'm new here.

I would like to ask some questions about my CM500 modem. I have been using this new modem for 2 months (Comcast ISP). Recently I installed a CCTV system at home and I want configure it to be able to monitor my cameras from outside of my network. For some reason I'm not having success with opening the necessary ports (80,443). I called my provider (Comcast) and they told me that as the modem was not provided by them they did not control forwarding ports(I'm pretty sure that the modem doesn't control forwarding ports, but they told me that). With my modem I'm using a NETGEAR N600 router to provide Wifi to home. Multiple times I tried to opened ports(forwarding ports) on my N600 router and everything seems to be fine but I still can not reach my CCTV system and a Wester Digital cloud device too. My question is: Can Comcast (ISP) have these ports blocked or can my router have any problems? I try resetting my router multiple times and when I open the ports it indicates that they are opened but still the problem continues.

Regards

Post data Sorry for my english, is not good:smileyvery-happy: