Management and Configuration Guide K/KA/KB.15.15

For PoE+, there must be 33 watts available for the module to begin supplying power to a port with
a PD connected. A slot in a zl chassis can provide a maximum of 370 watts of PoE/PoE+ power
to a module.
Disconnecting a PD from a PoE port makes that power available to any other PoE ports with PDs
waiting for power. If the PD demand for power becomes greater than the PoE power available,
power is transferred from the lower-priority ports to the higher-priority ports. (Ports not currently
providing power to PDs are not affected.)
Power priority operation
If a PSE 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, the
power allocation is prioritized to the ports that present a PD power demand. This causes the loss
of 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.
Power allocation is prioritized according to the following methods:
Priority class Assigns a power priority of low (the default), high, or criticalto
each enabled PoE port.
Port-number priority A lower-numbered port has priority over a higher-numbered port
within the same configured priority class, for example, port A1
has priority over port A5 if both are configured with high priority.
About assigning PoE priority with two or more modules
Ports across two or more modules can be assigned a class priority of low (the default), high, or
critical. For example, A5, B7, and C10 could all be assigned a priority class of Critical. When
power is allocated to the ports on a priority basis, the Critical priority power requests are allocated
to module A first, then Module B, then C, and so on. Next, the High priority power requests are
allocated, starting with module A, then B, then C, and the remaining modules in order. Any
remaining power is allocated in the same manner for the Low priority ports, beginning with module
A though the remaining modules. If there is not enough PoE power for all the PDs connected to
PoE modules in the switch, power is allocated according to priority class across modules.
Example
All ports on module C are prioritized as Critical.
(HP_Switch_name#) interface c1-c24 power-over-ethernet
critical
All ports on module A are prioritized as Low.
(HP_Switch_name#) interface a1-a24 power-over-ethernet
low
There are 48 PDs attached to all ports of modules A and C (24 ports each module); however, there
is enough PoE power for only 32 ports (8.5 watts × 32 ports=273 watts.) The result is that all the
Critical priority ports on module C receive power, but only 8 ports on module A receive power.
On module A, the port A1 has the highest priority of the ports in that module if all ports are in the
same priority class, which is the case for this example. Since a minimum 17 + 5 watts of power
is allocated per PoE module for PoE, port A1 will always receive PoE power. If another port on
module A had a higher priority class than port A1, that port would be allocated the power before
port A1.
For PoE+ modules there must be a minimum of 33 + 5 watts of power allocated per PoE+ module.
About PoE operation 125