Poe Operating Notes - HP ProCurve 6400cl Series Management And Configuration Manual

Power Over Ethernet (PoE) Operation for the Series 5300xl Switches

PoE Operating Notes

11-22
you can still fully populate the module with appliances. In this case, the lowest-
priority port will not receive power unless an appliance in a higher-priority
port is disconnected.
There is also a scenario where a device on a lower-priority port can experience
a power cycle (temporarily lose power) while a higher-priority port is bringing
up a PoE device. Suppose, for example, that:
1. An xl PoE module in slot B, with all ports configured at the default Low
priority, is receiving 204 watts of power from an EPS.
2. The 21 PoE devices on ports B2 - B22 draw 9.0 watts of power each (9 x
21 = 189), leaving 15.0 watts unused, which is less than the 15.4 watt
minimum needed to add another PoE device to the module. (Refer to "PD
Support" on page 11-6.)
3. The system operator plugs a 7.0-watt PoE device into port B1, which is
the highest-priority port in slot B.
In the above scenario, there is less than 15.4 watts available to support the
initial bringup of the newly installed device on port B1. As a result, port B22
(the lowest-priority port on the module) temporarily loses power so that there
is enough power to add the new device on port B1. After the new device begins
operation, the power demand on port B1 drops to 7 watts. At this point, there
are 20 devices consuming 9 watts each, and 1 device consuming 7 watts, for
a total of 187 watts, and the module now has 17 watts of unused power
available. Since this exceeds the minimum of 15.4 watts required to bring up
any PoE device, there is now enough power available to bring back up the
device on port B22.
PoE Operating Notes
■ Simply disabling a PoE port does not affect power delivery through
that port. To cycle the power on a PD receiving power from a PoE
port on the switch, disable, then re-enable the power to that port. For
example, to cycle the power on a PoE device connected to port 1 on
an xl PoE module installed in slot D:
HPswitch(config)# no interface d1 power
HPswitch(config)# interface d1 power