Or configure your model and disable all port forwarding rules.
Thats what i did and it made my life so much easier and restrictions free.
I also disabled firewall but that's optional because it easier to add ports exceptions to firewall then to modem caz some modems cant have more then couple of ports to be added to exception list due to little UI space or for some other reasons.
My comcast business modem could have i think 10 exceptions but i needed more because i had more games hosted, so i just dissabled the port forwarding rules at all for true static IP and
BAM all problems were GONE
