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Perpetual PoE and Fast PoE


Power over Ethernet (PoE) facilitates the flow of electric power over data cables. With PoE, powered devices can receive power from the same ports that are used to connect PCs to the network. Perpetual PoE and fast PoE deliver PoE more efficiently and predictably from the power sourcing equipment (PSE) device to the connected powered device (PD).

  • Perpetual PoE provides uninterrupted power to connected PDs even when the PSE switch is rebooting.

  • With fast PoE, the switch saves PoE power settings across a reboot. It powers on the PD once the PSE starts booting—within a few seconds of switching on power—without waiting for the boot process to complete.

Perpetual PoE and fast PoE are complementary features that work independently of each other. In cases where perpetual PoE cannot maintain uninterrupted power, such as a power cycle or failure, fast PoE helps to restore power to the PDs quickly.

Perpetual PoE does not maintain uninterrupted power in the following cases:

  • Power failure or power cycle.
  • PoE controller firmware update.
  • If LLDP power negotiation is enabled on a PoE interface, power to the PD on that interface will be interrupted even if perpetual POE is configured on the PSE. This is because the the OS must come online before LLDP packet exchanges between the PSE and PD can take place.

Perpetual PoE and fast PoE are disabled in the following cases:

  • System zeroization.
  • USB installation.
  • Loading the factory default configuration.

Configuring Perpetual PoE and Fast PoE

To configure perpetual PoE and fast PoE, use the following commands:

  • To configure perpetual PoE:

  • To configure fast PoE: