Open NAT Solution

I figured out a solution for my 2 xboxes not having an open NAT. It's not common knowledge but my ISP's cable modem supports up to 12 external IP addresses. I hooked up my cable modem to a 4 port ethernet switch and connected my two xboxes and my router to the switch. My PCs are connected to the router. After resetting the modem, each xbox got an external IP as did my router. The PCs got internal IPs and are protected from the big bad Internet by the router's firewall. After booting up both xboxes, the network tests both showed an open NAT. WooHoo! Success! Now I should have no problems in COD4 such as dropping when a match starts or people being unable to join my party.