3Com S7906E Configuration Manual page 2482

All PSEs implement the same PoE interface power management policies. When a PSE supplies power
to a PD,
If the PoE interface power management is not enabled, no power will be supplied to a new PD if
the PSE power is overloaded.
If the PoE interface power management priority policy is enabled, the PD with a lower priority is
first powered off to guarantee the power supply to the PD with a higher priority when the PSE
power is overloaded.
19 watts guard band is reserved for each PoE interface on the device to prevent a PD from being
powered off because of a sudden increase of the PD power. When the remaining power of the
PSE where the PoE interface resides is lower than 19 watts and no priority is configured for the
PoE interface, the PSE does not supply power to the new PD; when the remaining power of the
PSE where the PoE interface resides is lower than 19 watts, but priority is configured for the PoE
interface, the interface with a higher priority can preempt the power of the interface with a lower
priority to ensure the normal working of the higher priority interface.
If the sudden increase of the PD power results in PSE power overload, power supply to the PD on
the PoE interface with a lower priority will be stopped to ensure the power supply to the PD with a
higher priority.
If the guaranteed remaining PSE power (the maximum PSE power minus the power allocated to the
critical PoE interface, regardless of whether PoE is enabled for the PoE interface) is lower than the
maximum power of the PoE interface, you will fail to set the priority of the PoE interface to critical.
Otherwise, you can succeed in setting the priority to critical, and this PoE interface will preempt the
power of other PoE interfaces with a lower priority level. In the latter case, the PoE interfaces whose
power is preempted will be powered off, but their configurations will remain unchanged. When you
change the priority of a PoE interface from critical to a lower level, the PDs connecting to other PoE
interfaces will have an opportunity of being powered.
Configuration prerequisites
Enable PoE for PoE interfaces.
Configuration procedure
Follow these steps to configure PoE interface power management:
To do...
Enter system view
Configure PoE interface power
management priority policy
Enter PoE interface view
Use the command...
system-view
poe pd-policy priority
interface interface-type
interface-number
1-9
Remarks
—
Required
Not configured by
default.
—