If you have lost or forgot the login password of your Xfinity Router, you can locate the reset button on Xfinity Router and reset the device by following the series of steps mentioned under:
Turn on the router by connecting its power adapter to an electric socket and pressing the power button.
Once the router turns on, locate the reset button. You can find it at the rear end of the device.
Press and hold the reset button for about 10 seconds; release it.
You will notice that the status lights of the router go off and the device restarts.
You can now use the default login credentials of the router to gain access to the router admin console.