Just running the ipconfig does nothing, it just tells you what the IP address on the computer is along with the gateway, and some other info. You need to actually look at the IP info it gives you and see if it's the right one for your setup. It should match the IP of the gateway aside from the last 3 numbers and the gateway should be the IP of your Comcast device. You said you can ping the gateway IP, is that from this computer? Did you try rebooting the router and model?