3
Automatically when the switch sets the power usage of the device by using CDP power negotiation .
Use the first or second method in the previous list to manually configure the cutoff-power value by entering
the power inline consumption default wattage or the power inline [auto | static max] max-wattage command.
Power Consumption Values
You can configure the initial power allocation and the maximum power allocation on a port. However, these
values are only the configured values that determine when the switch should turn on or turn off power on the
PoE port. The maximum power allocation is not the same as the actual power consumption of the powered
device. The actual cutoff power value that the switch uses for power policing is not equal to the configured
power value.
When power policing is enabled, the switch polices the power usage at the switch port, which is greater than
the power consumption of the device. When you are manually set the maximum power allocation, you must
consider the power loss over the cable from the switch port to the powered device. The cutoff power is the
sum of the rated power consumption of the powered device and the worst-case power loss over the cable.
The actual amount of power consumed by a powered device on a PoE port is the cutoff-power value plus a
calibration factor of 500 mW (0.5 W). The actual cutoff value is approximate and varies from the configured
value by a percentage of the configured value. For example, if the configured cutoff power is 12 W, the actual
cutoff-value is 11.4 W, which is 0.05% less than the configured value.
We recommend that you enable power policing when PoE is enabled on your switch. For example, if policing
is disabled and you set the cutoff-power value by using the power inline auto max 6300 interface configuration
command, the configured maximum power allocation on the PoE port is 6.3 W (6300 mW). The switch
provides power to the connected devices on the port if the device needs up to 6.3 W. If the CDP-power
negotiated value or the IEEE classification value exceeds the configured cutoff value, the switch does not
provide power to the connected device. After the switch turns on power on the PoE port, the switch does not
police the real-time power consumption of the device, and the device can consume more power than the
maximum allocated amount, which could adversely affect the switch and the devices connected to the other
PoE ports.
How to Configure PoE
Configuring a Power Management Mode on a PoE Port
SUMMARY STEPS
1.
configure terminal
2.
interface interface-id
3.
power inline {auto [max max-wattage] | never | static [max max-wattage]}
4.
end
5.
show power inline [interface-id | module switch-number]
Catalyst 2960-XR Switch Interface and Hardware Component Configuration Guide, Cisco IOS Release 15.0(2)EX1
88 OL-29420-01
Configuring PoE
How to Configure PoE
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