What Is Power over Ethernet Used For?
Course Contents
1. Introduction to Power over Ethernet (PoE)
Power over Ethernet (PoE) is a networking technology that enables a single Ethernet cable to carry both data and electrical power. This innovation simplifies network deployments, especially in environments where installing separate power lines is costly or impractical.
So, what is Power over Ethernet used for in real-world networks?
It’s commonly used to power VoIP phones, IP surveillance cameras, wireless access points, and IoT devices all through the same cable that provides network connectivity. This makes PoE ideal for both enterprise environments and smart home setups.
Benefits of PoE in Networking
- Cost Efficiency
PoE eliminates the need for electrical outlets near each device, significantly reducing installation costs. - Simplified Cabling
By combining power and data into one cable, PoE reduces clutter and simplifies cable management. - Flexible Device Placement
Devices can be installed in hard-to-reach or outdoor locations, regardless of power outlet availability. - Centralized Power Management
Network administrators can control power remotely, enabling features like device rebooting, power scheduling and energy monitoring from the switch.
2. PoE Standards
IEEE 802.3af (PoE)
Introduced in 2003, IEEE 802.3af allows up to 15.4 watts of DC power per port from the Power Sourcing Equipment (PSE), with 12.95 watts available at the Powered Device (PD) after accounting for cable loss. It’s suitable for low-power devices like basic VoIP phones or small wireless APs.
IEEE 802.3at (PoE+)
Introduced in 2009, IEEE 802.3at (PoE+) delivers up to 30W of DC power per port from the PSE, with 25.5W available at the PD. This higher power output supports devices with greater energy demands, such as cameras with pan/tilt/zoom (PTZ) features.
IEEE 802.3bt (UPoE and UPoE+)
The IEEE 802.3bt standard extends power delivery even further:
- UPoE (Type 3) Supplies up to 60W per port using all four wire pairs in the Ethernet cable, suitable for video conferencing systems or larger wireless access points.
- UPoE+ (Type 4) Supplies up to 100W per port, enabling power delivery to devices like interactive displays and advanced IoT systems.
3. Components of PoE
Power Sourcing Equipment (PSE)
PSEs are the devices that supply power over Ethernet. These include PoE-enabled switches and PoE injectors. They automatically detect connected PDs and negotiate the required power level to ensure safe and efficient delivery.
Powered Devices (PD)
PDs are the endpoint devices that receive power. Examples include:
- VoIP phones
- IP cameras
- Wireless access points
- Access control panels
- IoT sensors
These devices must support PoE standards to be properly powered by a PSE.
4. PoE Practical Example
When a VoIP phone is connected to a PoE-capable switch, the switch detects it using a PoE handshake protocol. It then delivers the correct amount of power through the Ethernet cable, eliminating the need for a separate power adapter.
Verifying Power Delivery
To confirm that the VoIP phone is receiving power, use the following CLI command on a Cisco switch:
Switch# show power inline
Available: 370.0(w) Used: 15.0(w) Remaining: 355.0(w)
Interface Admin Oper Power Device Class Max
(Watts)
--------- ------ ---------- ------- ------------------- ----- ----
Fa0/0 auto on 10.0 IP Phone 7960 3 15.4
Fa0/1 auto off 0.0 n/a n/a 15.4
Fa0/2 auto off 0.0 n/a n/a 15.4
Fa0/3 auto off 0.0 n/a n/a 15.4
Fa0/4 auto off 0.0 n/a n/a 15.4
Fa0/5 auto off 0.0 n/a n/a 15.4
Fa0/6 auto off 0.0 n/a n/a 15.4
Fa0/7 auto off 0.0 n/a n/a 15.4
Fa0/8 auto off 0.0 n/a n/a 15.4
Fa0/9 auto off 0.0 n/a n/a 15.4
5. Conclusion
If someone asks you : What is Power over Ethernet used for ?
The answer is simple:
It’s used to power and connect network devices like VoIP phones, IP cameras, wireless access points, and IoT systems all through a single Ethernet cable, without the need for separate power sources !!