A Linksys router red light is a serious problem. Some of the possible causes are: power supply problems, overheating (check if the device has proper ventilation), hardware failure, or firmware. If the light is still on, visit the Linksys support website and look for troubleshooting for your specific router model. This should be performed after resetting the router to its factory defaults, after pressing and holding the reset button for a couple of minutes, usually 30 seconds. For more details, contact us.