- Link light on NIC or switch is steady on when NIC connected to another device. Off or flickering indicates connection problem.
- Activity light on NIC or switch turns on when card detects network traffic. No flicker when creating network traffic indicates a problem.
- Solid green light means connectivity, flashing green light means intermittent connectivity, no green light means no connectivity, flashing amber light means there are collision on the network.
- There may be another light to indicate the speed.
Some motherboards will also have indicator lights that can provide information while the computer is booting. Other motherboards may also have numeric POST codes displayed on the motherboard.
Power lights let you know if you’re receiving power from the power supply.