Check that the port actually provides PoE, that the switch has enough power left (its PoE budget), and that the device's PoE standard matches the switch. Long or poor-quality cables can also drop the power too low.
Common causes
Switch port doesn't supply PoE
Many switches only provide PoE on some ports, or not at all.
PoE budget exceeded
Each switch has a total power budget. Adding cameras or access points can exceed it, so some devices don't get power.
Standard mismatch
Devices needing PoE+ (802.3at, up to 30 W) or PoE++ (802.3bt) won't run on basic PoE (802.3af, 15.4 W).
Cable problems
Damaged cables, bad terminations, or very long runs reduce delivered power.
Passive vs. standard PoE
Some devices use passive PoE that isn't compatible with standard switches.
How to fix it, step by step
- 1
Confirm the port supplies PoE
Check the switch's specifications and port labels, or the PoE status in its management page.
- 2
Check the power budget
Add up the devices' power needs and compare to the switch's PoE budget.
- 3
Match the PoE standard
Check whether the device needs 802.3af, at, or bt, and that the switch supports it.
- 4
Test with a short cable
A short, known-good cable near the switch rules out the cable run.
- 5
Use an injector to test
A PoE injector of the right standard confirms whether the device itself works.
When to call a technician
We size PoE switches for your cameras, phones, and access points, run and terminate the cabling, and make sure everything has enough power with room to grow.
On-site support across Orange County · see our business networking and WiFi installation services.
Frequently asked questions
How far can PoE run?
Standard Ethernet and PoE are rated for up to 100 meters (328 feet) per cable run.
What's the difference between PoE and PoE+?
PoE (802.3af) provides up to 15.4 W per port; PoE+ (802.3at) provides up to 30 W. Many access points and PTZ cameras need PoE+.
Can PoE damage a device that doesn't need it?
Standard PoE switches check before sending power, so normal devices are safe. Passive PoE can damage devices that don't expect it.