• Disable or re-enable per-port PoE operation on individual ports to help control power usage and avoid
oversubscribing PoE resources.
• Configure per-port priority for allocating power in case a PoE device becomes oversubscribed and must drop
power for some lower-priority ports to support the demand on other, higher-priority ports.
• Manually allocate the amount of PoE power for a port by usage, value, or class.
• Allocate PoE power based on the link-partner’s capabilities via LLDP.
NOTE:
The ports support standard networking links and PoE links. You can connect either a non-PoE device
or a PD to a port enabled for PoE without reconfiguring the port.
PD support
To best utilize the allocated PoE power, spread your connected PoE devices as evenly as possible. Depending on
the amount of power the power supply device delivers to a PoE switch, there may or may not always be enough
power available to connect and support PoE operation on all the ports. When a new PD connects to a PoE switch
and the switch does not have enough power left for that port:
• If the new PD connects to a port “X” having a
higher
PoE priority than another port “Y” that is already
supporting another PD, then the power is removed from port “Y” and delivered to port “X”. In this case the PD
on port “Y” loses power and the PD on port “X” receives power.
• If the new PD connects to a port “X” having a
lower
priority than all other PoE ports currently providing power
to PDs, then power is not supplied to port “X” until one or more PDs using higher priority ports are removed.
In the default configuration (
usage
), when a PD connects to a PoE port and begins operating, the port retains
only enough PoE power to support the PD's operation. Unused power becomes available for supporting other PD
connections. However, if you configure the
poe-allocate-by
option to either
value
or
class
, all of the power
configured is allocated to the port.
For PoE (not PoE+), while 17 watts must be available for a PoE module on the switch to begin supplying power to
a port with a PD connected, 17 watts per port is not continually required if the connected PD requires less power.
For example, with 20 watts of PoE power remaining available on a module, you can connect one new PD without
losing power to any connected PDs on that module. If that PD draws only 3 watts, 17 watts remain available, and
you can connect at least one more PD to that module without interrupting power to any other PoE devices
connected to the same module. If the next PD you connect draws 5 watts, only 12 watts remain unused. With only
12 unused watts available, if you then connect yet another PD to a higher-priority PoE port, the lowest-priority port
on the module loses PoE power and remains unpowered until the module once again has 17 or more watts
available. (For information on power priority, see
on page 108.)
For PoE+, there must be 33 watts available for the module to begin supplying power to a port with a PD
connected.
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
When is power allocation prioritized?
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, then 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-
108
Aruba 2930F / 2930M Management and Configuration Guide
for ArubaOS-Switch 16.08
