What is POE (Power Over Ethernet) ?

POE is was developed to enable power together with data to be delivered to Powered Devices (PD) such as wireless APs, IP cameras.

As technology evolves, there are more PDs which require a higher input power. This is where we need to study more about the Power Sourcing Equipment (PSE) such as your switches, hubs or external POE injectors and whether they are the right fit (right number of ports and sufficient output power) for your existing infrastructure as demands continue such as wider Wi-Fi coverage which requires additional APs.

Currently based on IEEE standards, there are 4 different types of POE classes. 802.3af (POE), 802.3at (POE+), 802.3bt(POE++) and 802.3bt Type 4(POE++). Before your PSE can enable power transfer to the PD, the PSE performs a signature detection process to confirm the class of POE the PD can take in. Following which, a process known as classification takes place. The PD displays a classification signature which lets the PSE know how much power to output. If a PD does not display a signature to the PSE, it is class 0 and the input power must not be more than 13 W.

Common POE problems include the following:

1) PDs are not operating

2) PDs are reloading intermittently

These will be instances where it will be best to check on the power that is delivered by the PSE as well as the class advertised by the PD or even the medium which power is being delivered which is the Ethernet cable. Testers these days such as the Fluke Networks Microscanner POE, LinkIQ or NetAlly's LinkRunner or Etherscope nXG will be able to easily troubleshoot problems relating to POE as well as cabling.