Power Supply Modes

This section describes PoE power supply modes.

The FW supports two power supply management modes: automatic and manual. The advantages and disadvantages of the modes are as follows:

The automatic mode is easy to configure but does not support manual control over PD power-on or power-off.
Compared with the automatic mode, the manual mode involves more complicated configuration but brings fewer interface faults.

In automatic or manual mode, priorities (Critical, High, and Low) can be set on interfaces based on the importance of PDs. When power consumption increases sharply, the system preferentially supplies power to the PDs connected to the interfaces with the Critical priority, and secondly to the PDs connected to the interfaces with the High priority. The automatic and manual modes have different processing methods when power supply is triggered or the PSE power is insufficient. The following table lists the differences.

**Table 1** Differences between the automatic and manual modes
Power Supply Mode	Configuration Difference for Triggering Power Supply	Processing Difference When the PSE Power Is Insufficient	Example
Automatic mode	A PoE interface connects to a PD through an Ethernet cable. After PoE is enabled on the interface, the PD can be powered on.	When the power supply of the PSE is close to full load, power supply is determined based on interface priorities. The PSE preferentially supplies power to the PDs connected to the interfaces with the Critical priority, and secondly to the PDs connected to the interfaces with the High priority. If the interfaces have the same priority, the PSE preferentially supplies power to the PD connected to the interface with the smallest interface number.	For example, the power supply priority of GE0/0/1 is Critical, and the interface has a PD connected. When the power supply provided by the PSE is fully loaded, the PSE powers off the PD connected to the interface with the lowest power supply priority and supplies power to the PD connected to GE0/0/1. If the power supply priorities of interfaces are the same, the PSE powers off the PD connected to the interface with the largest interface number.
Manual mode	A PoE interface connects to a PD through an Ethernet cable. In addition to enabling PoE on the interface, you need to manually power on the interface, so that the PD connected to the interface can be powered on.	When the power supply of the PSE is close to the full load, the PSE cannot power on more PDs. To let the PSE supply power to a new PD, you must power off an existing PD.	For example, the power supply priority of GE0/0/1 is Critical, and the power supply provided by the PSE is fully loaded. When a PD connects to GE0/0/1, the PSE generates an alarm to indicate the PD connection, but does not supply power to the PD. The PSE supplies power to the PD only after another PD is manually powered off.