I have had issues in the past with being able to port forward with comcast "ISP",
I would like to know if anyone has comcast and has been able to port-forward,
@SugarD-x and I have talked about it in the past and he believes somewhere around the guidelines that there is a block from comcast when port-forwarding.
This is a bigger community and there might be an individual that can confirm it, Comcast gives no technical support for port-forwarding.
Therefore I hope someone has encountered this issue and has found away around it. I would like to find a fix for this by January
http://forums.xfinity.com/t5/Your-Home-Network/Port-Forwarding/m-p/1227575#M89448
Its not your ISP, its your router doing that...
There's absolutely no connection with VC:MP, and since this is a VC:MP forum this gets a lock.
Like you said, it's a big company. So I'm positive there's more then enough reference material online for your problem.