What Is PoE (Power over Ethernet)?
PoE (Power over Ethernet) — a technology that delivers electrical power through the same Ethernet cable that carries data — powering devices like IP phones, wireless APs and cameras without separate power supplies.
How it works
A PoE-capable switch injects DC power onto the data cable pairs. Standards define budgets: 802.3af (~15W), 802.3at/PoE+ (~30W), and 802.3bt (60–90W) for demanding devices. The switch negotiates with the powered device to deliver only what it needs — non-PoE devices connected to the same port simply receive no power.
Why it matters
PoE is why modern offices deploy phones, APs and cameras anywhere a network cable reaches — no electrician required per device. Switch PoE budget planning (total watts across all ports) is a genuine design consideration and appears in CCNA wireless/infrastructure topics.
Frequently asked questions
What devices use PoE?
IP phones, wireless access points, security cameras, door controllers and IoT sensors — anything benefiting from a single cable for both data and power.
What are the PoE standards and their power levels?
802.3af (~15W), 802.3at/PoE+ (~30W) and 802.3bt (60–90W) — newer standards power more demanding devices.
Can PoE damage a non-PoE device?
No — the switch negotiates before delivering power; a device that doesn't request PoE just receives normal data with no power applied.
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