What does POE mean in a network context?

• A. Protected Optical Ethernet
• B. Port over Ethernet
• C. Power on Ethernet
• D. Power over Ethernet

Answer: (D)

Power over Ethernet means delivering electrical power to networked devices over the same Ethernet cable that carries data. This lets devices like IP cameras, VoIP phones, and wireless access points run from a single cable instead of needing a separate power supply. The power is provided by a Power Sourcing Equipment (a PoE switch or injector) and negotiated with the device on the other end (the powered device) to ensure safe delivery. Standards such as IEEE 802.3af, 802.3at, and 802.3bt define how much power can be sent per port and how devices detect and classify themselves so non-PoE equipment isn’t affected. There are different ways power can be carried—either on the data pairs used for signaling or on the spare pairs—depending on the Ethernet standard in use. PoE is convenient for reducing cabling and enabling centralized power management, but you need to match power budgets and cable capabilities to the devices being powered.