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NETWORKING · POWER

Active vs Passive PoE: What Is the Difference?

Active PoE follows the IEEE 802.3af/at/bt standards and negotiates voltage with the device before supplying power, typically 48 V DC. Passive PoE is non-standard: it sends a fixed voltage, often 24 V DC, with no negotiation, so it can damage a device expecting active PoE.

01

The Short Answer

Active PoE is the IEEE-standard kind: before any power flows, the source and the device perform a handshake to agree the voltage and power class, so a device only ever receives what it can take. Passive PoE skips the handshake and applies a fixed voltage to the line regardless of what is connected.

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    Negotiation Active negotiates; passive does not.
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    Voltage Active ~48 V DC; passive often a fixed 24 V DC.
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    Compliance Active follows IEEE 802.3af/at/bt; passive does not.
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    Risk Passive power into a device expecting active PoE can damage it.
02

What We Recommend

For interoperable, protected deployments, specify active, standards-compliant PoE end to end. Passive PoE has a place in closed, known systems, but it should never be mixed with standard PoE equipment without care.

See our guide to industrial Power over Ethernet for the full picture.