Power over Ethernet (POE)
Power over Ethernet (PoE)
Power over Ethernet (PoE) is a technology that allows a single Ethernet cable to carry both:
Network data
Electrical power
This means devices can receive power and network connectivity through the same cable.
Why Use PoE?
Without PoE:
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IP Camera
|
Power Outlet
|
Ethernet Cable
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You need both a power cable and a network cable.
With PoE:
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PoE Switch
|
Ethernet Cable
|
IP Camera
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Only one cable is needed.
Devices That Commonly Use PoE
IP Cameras
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PoE Switch → Security Camera
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Common in surveillance systems.
Wireless Access Points (WAPs)
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PoE Switch → Wi-Fi Access Point
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Useful when mounted on ceilings.
VoIP Phones
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PoE Switch → IP Phone
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No separate power adapter required.
IoT Devices
Sensors
Badge readers
Smart building equipment
How PoE Works
A PoE switch or PoE injector sends power over the Ethernet cable.
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PoE Switch
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CAT6 Cable
|
Powered Device
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The device receives:
Data
Electrical power
at the same time.
PoE Components
PSE (Power Sourcing Equipment)
The device that provides power.
Examples:
PoE Switch
PoE Injector
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PSE → Power Source
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PD (Powered Device)
The device receiving power.
Examples:
IP Camera
VoIP Phone
Wireless Access Point
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PD → Receives Power
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PoE Injector
Used when a switch does not support PoE.
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Switch
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Injector
|
IP Camera
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The injector adds power to the Ethernet cable.
PoE Standards
IEEE 802.3af (PoE)
Up to 15.4 Watts per port
Common for:
VoIP phones
Small access points
IEEE 802.3at (PoE+)
Up to 30 Watts per port
Common for:
Security cameras
Advanced access points
IEEE 802.3bt (PoE++)
Up to 60 Watts or 90-100 Watts (depending on type)
Common for:
PTZ cameras
Video conferencing systems
Digital signage
PoE Distance Limitation
Like normal Ethernet:
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100 meters
(328 feet)
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Maximum standard cable distance.
Advantages of PoE
✅ One cable for power and data
✅ Lower installation cost
✅ Easier cable management
✅ No local power outlet needed
✅ Simplifies deployments
✅ Centralized power management
PoE Switch Example
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+-- IP Camera
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PoE Switch ---+-- Access Point
|
+-- VoIP Phone
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The switch powers all devices through Ethernet cables.
PoE vs Non-PoE
Feature PoE Non-PoEData Transmission Yes Yes
Power Delivery Yes No
Separate Power Cable Needed No Yes
Installation Cost Lower Higher
Common for Cameras/APs Yes No
Network+ Exam Tips
Remember These Terms
PoE
Power and data on one Ethernet cable
PSE
Power Sourcing Equipment
Provides power
PD
Powered Device
Receives power
Common PoE Devices
IP Cameras
VoIP Phones
Wireless Access Points
IoT Devices
Power Standards
Standard Max Power802.3af 15.4W
802.3at (PoE+) 30W
802.3bt (PoE++) 60W-100W
Quick Memory Trick
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PoE = Power + Ethernet
PSE = Supplies Power
PD = Powered Device
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Simple definition: Power over Ethernet (PoE) is a technology that delivers both electrical power and network data over a single Ethernet cable, allowing devices such as IP cameras, VoIP phones, and wireless access points to operate without a separate power connection.
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