System information

11-5
Power Over Ethernet (PoE) Operation
Power Availability and Provisioning
Power Priority
In the default configuration PoE power priority is determined by port number,
with the lowest numbered port having the highest priority.
When Does the Switch Prioritize Power Allocations? If the switch can
provide power for all existing PD demands, it does not use its power priority
settings to allocate power. However, if the PD power demand oversubscribes
the available power, then the switch prioritizes the power allocation to the
ports that present a PD power demand. This causes the switch to remove
power from one or more lower-priority ports to meet the power demand on
other, higher-priority ports. (This operation occurs, regardless of the order in
which PDs connect to the switch’s PoE-configured ports.)
How Does the Switch Prioritize Power Allocations? The switch
simultaneously uses two priority methods:
■ The priority class method enables port PoE priority class assign-
ments of Low (the default), High, and Critical.
■ The port-number priority method gives a lower-numbered port
priority over a higher-numbered port within the same configured
priority class.
The ports configured with the highest priority of either bank will receive PoE
power, regardless of position. There is also an option to provision ports with
additional power by adding an external power supply. For more information
on using external power supplies with PoE-capable switches, refer to the PoE
Planning and Implementation Guide.
Table 11-1 provides examples of how PoE priority settings impact operation.
Table 11-1. Example of PoE Priority Operation on the ProCurve 2510-48-PWR
Port Priority
Setting
Configuration Command
1
and Resulting Operation
25 - 48 Critical This priority class always receives power. If there is not enough power to provision PDs on
all of the ports configured for this class, then no power goes to ports configured for High and
Low priority. If there is enough power to provision PDs on only some of the “Critical” ports,
then power is allocated to the “Critical” ports in ascending order, beginning with the lowest-
numbered port in the class, which, in this case, is port 25. For this example, the CLI command
to set ports to “Critical” is:
ProCurve(config)# interface e 25-48 power critical