Power over Ethernet
For switch without built-in power injector, you will need to purchase the external power injector to support PoE enable device. External power injector device is not configurable, it usually comes with fixed voltage. Cisco PoE enabled switches provide flexibility to adjust power required for your IP-based devices (AP and/or IP phones)
802.3af
Provides up to 15.4W power, minimum 44VDC and 350mA.
12.95W is assured at the powered device, this is taken into account that power was dissipated in the cable.
At least a standard CAT5e cable is required for PoE.
Class selector
Class 0 (default) 15.4W (PSE), 0.44 ~ 12.95W (PD)
Class 1 (very low power) 4.0W(PSE), 0.44 ~ 3.84W(PD)
Class 2 (low power) 7.0W(PSE), 3.84 ~ 6.49W (PD)
Class 3 (Mid power) 15.4W(PSE), 6.49 ~ 12.95W(PD)
Class 4 (High power) Reserved.
PSE – Power Sourcing Equipment, power provider.
PD – Powered device.
Configuration
Switch(config)#interface fa0/24
Switch(config-if)#power inline auto
Switch(config-if)#end
Auto is the default option, this option automatically detects power required by the powered device.
Switch(config-if)#power inline never
Never keyword implies no power will be supplied nor will there be auto detection.
Switch(config-if)#power inline max 15400
Max keyword specifies the maximum allowable Watt for the interface, the value is expressed in milliwatts, in this example the maximum Wattage is 15.4W or 15400mW
Manual power supply configuration
Switch(config-if)#power inline consumption default 5000
Meaning the interface will use the default 5W instead of auto-detection to determine the power needed to supply to PD.
Switch(config-if)#power inline consumption 5000
Manually set the power consumption on the specific interface instead of auto-detection to determine the power needed to supply to PD.
Since auto-detection is possible with CDP, it is recommended to disable CDP when using manual power supply configuration.
Power Policing modes
Logging: When power violation occurs (i.e. when powered device is using more power than allocated) port restarts and a log is sent, device is powered up.
Err-disabled: When power violation occurs, port is put to error disabled state, a manual shutdown and no shutdown command is required to enable the port.
Switch(config-if)#power inline police
Switch(config-if)#end
power inline police is the same as power inline police action errdisable command, the default is errdisable.
Switch(config-if)#power inline police action log
Configures the power policing mode as logging.
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