From RSI - Robotic Systems Integration - SynqNet Systems
Ethernet LEDs
The Ethernet port has two LEDs: Link/Act and 10/100. The Link/Act LED should be ON at each end of the Ethernet cable. If the Link/Act LED is not ON, it usually indicates that there is a bad connection or a bad cable. See the table below for the meaning of each LED and its state.
Information taken from Danaher Motion.