Networking Guides

PoE Standards Explained: 802.3af vs 802.3at vs 802.3bt — Lebanon Guide

Published by HI-GAIN Engineering Team on April 10, 2026

Power over Ethernet: The Foundation of Modern Networking

Power over Ethernet (PoE) delivers electrical power alongside data over standard Ethernet cables, eliminating the need for separate power adapters at each device location. In Lebanon, where running additional power outlets is often impractical in concrete buildings and power management during outages is critical, PoE simplifies installations and centralizes power backup through UPS-protected switches.

Three IEEE standards define how PoE works. Understanding the differences is essential for selecting compatible equipment and avoiding power-related issues in your network.

The Three PoE Standards

802.3af — PoE (Original, 2003)

  • Maximum PSE output: 15.4 watts per port
  • Maximum PD power available: 12.95 watts (after cable losses)
  • Voltage: 44-57V DC
  • Cable pairs used: 2 of 4 pairs
  • Typical devices: Standard IP cameras (fixed lens), basic WiFi access points, VoIP phones, small IoT sensors

802.3af is sufficient for the majority of network devices. Most access points from MikroTik and Ubiquiti, including the cAP AX and U6 Pro, operate within 802.3af power limits.

802.3at — PoE+ (2009)

  • Maximum PSE output: 30 watts per port
  • Maximum PD power available: 25.5 watts
  • Voltage: 50-57V DC
  • Cable pairs used: 2 of 4 pairs
  • Typical devices: High-performance APs (like U7 Pro), PTZ cameras, outdoor APs with heaters, video conferencing units, thin client PCs

802.3at provides double the power of 802.3af, enabling more powerful devices. The Ubiquiti U7 Pro and some outdoor APs require PoE+ for full functionality. 802.3at is backward compatible — a PoE+ port safely powers 802.3af devices at the lower power level.

802.3bt — PoE++ (2018)

  • Type 3: Up to 60 watts PSE output (51W at PD)
  • Type 4: Up to 90 watts PSE output (71.3W at PD)
  • Voltage: 50-57V DC
  • Cable pairs used: All 4 pairs
  • Typical devices: High-power PTZ cameras with heaters and wipers, digital signage displays, small switches, point-of-sale terminals, LED lighting panels

802.3bt is less common in standard networking but important for specialized devices. Some advanced PTZ cameras and PoE-powered displays require Type 3 or Type 4 power.

Passive PoE vs Standard PoE

Important distinction: MikroTik and some other manufacturers also use passive PoE (non-standard) at various voltages:

  • MikroTik 24V passive PoE: Used by many older MikroTik devices and some current entry-level models. Not compatible with standard 802.3af/at switches. Requires MikroTik PoE injectors or MikroTik switches with passive PoE output.
  • MikroTik 48V passive PoE: Closer to standard PoE voltage but without the negotiation handshake. Works with some 802.3af devices but not guaranteed.
  • Ubiquiti 24V passive PoE: Used by older Ubiquiti airMAX devices. Requires Ubiquiti PoE adapters.

The MikroTik PoE Adapter 24V 1.25A provides passive 24V PoE for devices requiring this non-standard voltage. Always check your device's PoE specification before connecting it to a switch or injector.

PoE Power Budget Explained

A PoE switch has a total power budget shared across all ports. The budget must exceed the combined power draw of all connected devices. Example calculations:

Small Office with 8 Devices

  • 4x UniFi U7 Pro APs at 15W each = 60W
  • 3x IP cameras at 10W each = 30W
  • 1x VoIP phone at 5W = 5W
  • Total: 95W
  • Recommended switch: MikroTik CSS610-8P-2S+IN (140W budget) — 45W headroom

Medium Office with 20 Devices

  • 8x UniFi U7 Pro APs at 15W each = 120W
  • 8x IP cameras at 10W each = 80W
  • 4x VoIP phones at 5W each = 20W
  • Total: 220W
  • Recommended switch: MikroTik CRS328-24P-4S+RM (500W budget) — 280W headroom

Always maintain at least 20% headroom above calculated PoE draw. This accounts for power spikes during device boot, firmware updates, and future device additions.

PoE and Cable Length

PoE power decreases with cable length due to resistance losses in the copper conductors. Key facts:

  • Maximum Ethernet cable length: 100 meters (as per 802.3 standard)
  • Power loss at 100 meters on Cat5e: approximately 4.5W for a 15.4W device
  • Power loss at 100 meters on Cat6: approximately 3.0W (lower resistance)
  • For 802.3bt devices requiring 60-90W, use Cat6A cable and keep runs under 80 meters for reliable power delivery

In Lebanese buildings where cable runs through concrete walls often take indirect routes, actual cable lengths can be 30-50% longer than the straight-line distance. Always measure or estimate actual cable length, not room-to-room distance.

PoE Injectors and Adapters

When your switch does not provide PoE, or you need to power a single device in a remote location, PoE injectors add power to an existing Ethernet cable:

Where to Buy PoE Equipment in Lebanon

HI-GAIN stocks PoE switches, injectors, and adapters from MikroTik and Ubiquiti at our Dora, Beirut warehouse. We help you calculate PoE budgets, select the right switch, and avoid compatibility issues. Check PoE equipment availability or call +961 3 337 666.

Frequently Asked Questions

What is the difference between PoE and PoE+?
PoE (802.3af) delivers up to 15.4W per port — sufficient for basic cameras and access points. PoE+ (802.3at) delivers up to 30W per port — needed for high-performance APs, PTZ cameras, and outdoor devices. PoE+ is backward compatible with PoE devices.
Can I use a PoE switch with non-PoE devices?
Yes. PoE switches detect whether the connected device supports PoE before sending power. If you plug a laptop or non-PoE device into a PoE port, the switch will not send power — only data. This is safe and standard behavior for 802.3af/at/bt compliant switches.
What PoE standard do Ubiquiti UniFi APs need?
Most UniFi APs work with 802.3af PoE. The U7 Pro and U7 LR require 802.3at PoE+ for full performance. The U7 Outdoor uses 802.3at. Check the specific model's datasheet — Ubiquiti always lists the required PoE standard.
What is passive PoE on MikroTik devices?
Passive PoE is a non-standard power delivery method used by MikroTik at 24V or 48V without the IEEE 802.3af/at negotiation handshake. Devices requiring passive PoE must use MikroTik PoE injectors or MikroTik switches with passive PoE output — do not connect them to standard 802.3af/at PoE ports.
Where can I buy PoE switches and adapters in Lebanon?
HI-GAIN stocks PoE switches from 8 to 48 ports, PoE injectors, and adapters from MikroTik and Ubiquiti at our Dora, Beirut warehouse. We provide compatibility advice and power budget calculations. Visit hi-gain.net or call +961 3 337 666.