H3C S5120-EI Series Operation Manual page 1026

All PSEs implement the same PD power management policies. When the PSE supplies power to a
PD,
By default, no power will be supplied to a new PD if the PSE power is overloaded.
Under the control of a priority policy, the PD with a lower priority is first powered off to guarantee
the power supply to the new 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 sudden increase of the power of the PD. When the remaining power of the
interface is lower than 19 watts and no priority is configured for a PoE interface, the PSE does not
supply power to the new PD; when the remaining power of the interface is lower than 19 watts, but
priority is configured for a 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 power of the PD results in PSE power overload, power supply to the
PD on the PoE interface with a lower priority will be stopped.
If the guaranteed remaining PSE power (maximum PSE power – 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 PD power management:
To do...
Enter system view
Configure the power
priority for the PoE
Configure
interface in PoE
the power
interface view
priority for
Configure the power
a PoE
priority for the PoE
interface
interface in PoE
configuration file view
Use the command...
system-view
interface interface-type
interface-number
poe priority { critical | high | low }
poe-profile profile-name [ index ]
poe priority { critical | high | low }
1-5
Remarks
—
Use either
command.
By default, the
power priority of a
PoE interface is
low.