What happens when an active Ethernet switch fails to sense a power over Ethernet (PoE) device on a port?

When an active Ethernet switch fails to sense a Power over Ethernet (PoE) device on a port, it switches off the direct current (DC) voltage on that port. This is because PoE switches are designed to provide power only when they detect a compatible PoE device connected to that specific port. If no such device is detected, the switch will automatically disable power delivery to conserve energy and ensure that power is utilized efficiently. This capability helps prevent potential damage to devices that are not designed to accept PoE and also helps maintain the overall system's power efficiency.

In contrast, increasing power to the port would be unnecessary and could lead to issues, while continuing to send data without interruption would not accommodate the requirements of PoE devices. Generating an alert for the network administrator may be useful but is not the default behavior of the switch in this scenario. The primary function is to manage power delivery based on device detection.