Budgeting Power for Devices Connected to a PoE Port
When Cisco powered devices are connected to PoE ports, the switch uses Cisco Discovery Protocol (CDP)
to determine the CDP-specific power consumption of the devices, and the switch adjusts the power budget
accordingly. This does not apply to IEEE third-party powered devices. For these devices, when the switch
grants a power request, the switch adjusts the power budget according to the powered-device IEEE classification.
If the powered device is a class 0 (class status unknown) or a class 3, the switch budgets 15,400 mW for the
device, regardless of the CDP-specific amount of power needed. If the powered device reports a higher class
than its CDP-specific consumption or does not support power classification (defaults to class 0), the switch
can power fewer devices because it uses the IEEE class information to track the global power budget.
By using the power inline consumption wattage interface configuration command or the power inline
consumption default wattage global configuration command, you can override the default power requirement
specified by the IEEE classification. The difference between what is mandated by the IEEE classification and
what is actually needed by the device is reclaimed into the global power budget for use by additional devices.
You can then extend the switch power budget and use it more effectively.
You should carefully plan your switch power budget, enable the power monitoring feature, and make
certain not to oversubscribe the power supply.
Caution
When you manually configure the power budget, you must also consider the power loss over the cable
between the switch and the powered device.
Note
Budgeting Power to All PoE ports
Perform this task to configure the amount of power budgeted to a powered device connected to each PoE port
on a switch:
SUMMARY STEPS
1.
configure terminal
2.
no cdp run
3.
power inline consumption default wattage
4.
end
5.
show power inline consumption default
DETAILED STEPS
PurposeCommand or Action
Enters global configuration mode.configure terminal
Example:
Switch# configure terminal
Step 1
Catalyst 2960-XR Switch Interface and Hardware Component Configuration Guide, Cisco IOS Release 15.0(2)EX1
90 OL-29420-01
Configuring PoE
Budgeting Power for Devices Connected to a PoE Port
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