The router reset button is located on the back of the router. The reset button is small and recessed and is normally a different color than the rest of the gateway's housing.
For example, if the gateway is black, the button is likely orange or yellow. This makes it easier to identify.
Using a paper clip or pen, gently depress the reset button and hold it until the lights on the front of the modem turn off. Once the lights turn off, release the button.
Comcast offers a router to all of its internet customers for a monthly fee. If your Comcast router isn't working, there may be something you can do to fix it.