You can configure Perpetual PoE or Fast PoE before physically connecting any endpoint.

After all configurations are completed, it is advised to do a manual shut and no-shut of the ports.

During an PSE firmware upgrade, power to the ports is interrupted. The switch backs up power configurations and reloads them after the IOS software restarts.

During a Micro Controller Unit (MCU) firmware upgrade, power to the ports is interrupted. After the upgrade, ports restore power immediately.

When switches are power-stacked, perpetual PoE and Fast PoE may not function as expected because of a power budget shortage.

If the powered device does not support LLDP, configure it with IEEE 802.3bt to provide the required power as specified for the device.

For devices that have negotiated a custom power level using LLDP, after the switch recovers from a power outage, Fast PoE restores power based only on initial detection of the powered device and its power classification. LLDP-based power negotiation requires Cisco IOS to be fully operational to exchange LLDP packets and communicate power requirements. Fast PoE quickly applies power using the initial detection and power classification to minimize downtime. The custom LLDP-negotiated power settings are re-established only once the IOS and LLDP exchange are operational again.