Power over Ethernet (PoE) delivers power, as well as data, over an Ethernet cable.

By default, a switch delivers PoE only when fully booted. And by default, when you reboot your switches, all your PoE devices connected to them must reboot.

This behavior may be acceptable when you’re only dealing with phones or Wi-Fi antennas, but it becomes annoying when you’re dealing with specific devices that may require manual actions after a reboot (biomedical, IoT, etc.), or when you simply want to reduce downtime. To meet this need, Extreme Networks offers two PoE features: Fast PoE and Perpetual PoE.

• Fast PoE: As soon as your switch starts up, it delivers power to the devices that require it. You no longer have to wait for your switch to be up and running before it delivers power. This means your devices start up at the same time as your switch, reducing the downtime perceived by the user.
  
• Perpetual PoE: When you restart your switch, it doesn’t cut off the PoE power supply. As a result, your devices don’t have to reboot, and can be reached again on the network as soon as the switch’s data plane is operational.

Let’s take a PoE phone as an example: