Power Over Ethernet (PoE)

Origins

Cisco invented Cisco Inline Power on the year 2000. Switches were called Power Sourcing Equipments (PSE) and the devices which uses the power were called Powered Device (PD).

IEEE Brought Cisco Inline Power to an standard, PoE on 2003. it was called 802.af.

PoE Types

TypeStandard NameNameWattageYear Released
Type 1PoE802.af15.4W2003
Type 2PoE+802.at30W2009
Type 34PPoE802.bt60W2011
Type 44PPoE802.bt90W2018

Active PoE

  • Delivers only the power needed by the Devices
  • Uses CDP or LLDP which stands for Cisco Discovery Protocol and Link Layer Discovery protocol respectively.
  • Most Cisco switches supports both Discovery Protocols

Passive PoE

  • Passive is Always-on Power
  • Its mostly called 24VPoE
  • Many Legacy equipments don't support CDP or LLDP

Device Classes

ClassStandardPSE OutputPD InputPoE Type
Class 0802.af15.4W12.94W1
Class 1802.af4W3.84W1
Class 2802.af7W6.49W1
Class 3802.af15.4W12.95W1
Class 4802.at30W25.5W2
Class 5802.bt45W40W3
Class 5802.bt60W51W3
Class 5802.bt75W62W4
Class 5802.bt90W73W4


If a device attempts to draw more power than the port configured to provide, a syslog message will be issued and the port will be shutdown and enter error-disabled state

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