Passive versus Active Power over Ethernet

Published: Wednesday, Oct 7, 2020 Last modified: Monday, Nov 23, 2020

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:

  1. 802.3af (802.3at Type 1) “PoE”
  2. 802.3at Type 2 “PoE+”
  3. 802.3bt Type 3 “4PPoE”[24]/“PoE++”
  4. 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

RBGPOE 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.