Poe Pinout RJ45

RJ45 connector with labeled pins for PoE configuration

PoE pinout RJ45 specifies which wires in an Ethernet cable carry both data and power for Power over Ethernet (PoE) systems. Standard Ethernet uses four twisted pairs (eight wires) while PoE repurposes unused pairs for DC power.

How PoE Pinout Works

PoE injects 48V DC alongside data signals using alternate wire pairs. The IEEE 802.3af/at standards define two modes:

Mode A: Uses data pairs (1/2, 3/6) for power alongside data
Mode B: Uses spare pairs (4/5, 7/8) exclusively for power

Most modern PoE devices support both modes via auto-sensing.

Main PoE Pin Configurations

Mode	Power Pins	Data Pins
Mode A	1 (+), 2 (-), 3 (+), 6 (-)	All 8 wires
Mode B	4 (+), 5 (-), 7 (+), 8 (-)	1-2, 3-6

Common Misconceptions

Contrary to popular belief, PoE doesn't require special cables beyond Cat5e or better. Standard Ethernet cables work fine for PoE+ (up to 25.5W) and PoE++ (up to 90W) when properly wired.

One often-overlooked fact: PoE injectors and switches perform power negotiations before sending voltage, preventing damage to non-PoE devices.

Fully Worked Example

For a security camera installation:

Use Cat6 cable supporting 10Gbps and 60W PoE++
Wire pins 1, 2, 3, 6 for both data and power (Mode A)
Connect to a PoE++ switch (IEEE 802.3bt) rated for 90W output
Verify connection with network analyzer showing 56V DC on pins 1/2

Why This Matters

Correct PoE pinout prevents voltage drop and ensures reliable power delivery. Improper wiring can cause:

Intermittent connectivity
Reduced power capacity
Device damage from improper voltage

Always verify pin configurations match your PoE devices' specifications.