Passive versus Active Power over Ethernet
Non-standard Passive != Standard Active Power over Ethernet
Published: Wednesday, Oct 7, 2020 Last modified: Monday, Dec 9, 2024
My hAP ac2 aka RBD52G-5HacD2HnD-TC has an ability to power it through Ethernet:
| Details | |
|---|---|
| PoE in | Passive PoE |
| PoE in input Voltage | 18-28 V |
| Number of DC inputs | 2 (DC jack, PoE-IN) |
| DC jack input Voltage | 12-30 V |
| Max power consumption | 21 W |
| Max power consumption without attachments | 16 W |
| FAN count | Passive |
Now if if I connect it to my UniFi Switch 8 POE-60W aka US-8-60W, it’s unable to power the device. Why?
Passive != Active PoE
The US-8-60W only supports 802.3af which is Active POE and 48V.
Interestingly upon Wikipedia Power over Ethernet page, Passive PoE is considered Non-standard!!
Actually 802.3af has several enhancements:
- 802.3af (802.3at Type 1) “PoE”
- 802.3at Type 2 “PoE+”
- 802.3bt Type 3 “4PPoE”[24]/“PoE++”
- 802.3bt Type 4 “4PPoE”/“PoE++”
See https://en.wikipedia.org/wiki/Power_over_Ethernet#Standard_implementation for more details.
Solutions
Use a passive PoE injector
Use another switch that can do Passive as well as Active
For example the US-8-150W can do Passive PoE as well as Active.
However do note the US-8-150W is 200USD versus the US-8-60W at ~109USD. Almost twice the price to get a switch that support both forms of PoE!!
Credit to brwainer on Reddit.