Power Priority Operation - HP ProCurve 6400cl Series Management And Configuration Manual

Power Over Ethernet (PoE) Operation for the Series 5300xl Switches
General PoE Operation
11-8

Power Priority Operation

When Does an xl PoE Module Prioritize Power Allocations? If an xl
PoE module can provide power for all connected PD demand, it does not use
its power priority settings to allocate power. However, if the PD power
demand oversubscribes the available power, then the module prioritizes the
power allocation to the ports that present a PD power demand. This causes
the module 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 module's PoE-enabled
ports.) Note that each PoE xl module is a stand-alone priority domain. The
switch does not prioritize one PoE module over another.
How Does an xl PoE Module Prioritize Power Allocations? xl PoE
modules apply the following priority scheme:
■ Using a priority class method, the module assigns a power priority
of Low (the default), High, or Critical to each enabled PoE port.
■ Using a port-number priority method, the module gives a lower-
numbered port priority over a higher-numbered port within the same
configured priority class.
Suppose, for example, that you configure the PoE priority for a module in slot
C as shown in table 11-2.