Can I get some help from a Comcast Expert please? I reported that my ethernet ports had gone down on our modem / router about three hours ago and was told there was system outage in our area so they couldn't probe the box. Weird, 'cause we still had / have wireless service. Anyhow they said I would get a call back at 5pm PST... I'm still waiting to hear back.
Powercycle the device for starters (the old turn it off and turn it on again thing). If that does not work then you'll need to do a factory reset. There is a little pinhole on the back. Use a paper clip or similar tool and depress the button for 30 seconds. You'll lose any custom settings. If your ports are still not working, then you'll need to swap the device.