Sam has an ARRIS cable modem and when he's plugged it into his router, he's not sure what the lights mean. Leo says that one is for connecting to the cable company for internet access. If it's off, he's not getting access. There's also a "link light" which will be solid when connected via ethernet, and when data goes back and forth, it blinks. Then there's the uplink and downlink lights. The manual should tell him what they mean. If one is off, then he'll know where the problems are.