I’m trying to power in RB5009Upr from another RB5009Upr PoE out using RBGPOE, but its giving Voltage too high error. If i connect directly without involving RBGPOE, then its fine. In both the cases, there is no additional devices connected to 2nd RB5009.
What could be the issue?
The RBGPOE gets detected as a low-voltage device, so if you are using a 48V PSU, the RB5009 will report “voltage too high” on its PoE-out port.
What’s the reason you want to use the RBGPOE? Are you trying to extract the DC jack from the injector and power the second RB5009 via DC?
To do that, you need to set PoE-Out to forced-on.
If you want it to work in auto-on mode, you would need to solder a 24 kΩ resistor between the DC-plug cables of the RBGPOE (do this at your own risk — it’s not officially supported and can potentially damage your devices).
You seemingly somehow missed:
"... notwithstanding being clearly marked on the case and in specs as being 18-57V compatible ..."
https://mikrotik.com/product/RBGPOE
Maybe adding this info to the product page explaining how it is not compatible with "high voltage PoE Auto-on setting" would help people
The issue only arises when you try to use it in reverse as a PoE extractor. The original poster likely wants to do this to get PoE-Out from a second RB5009, since powering it from the PoE-In port would result in a “no_valid_psu” error on its PoE-Out ports. In this reverse scenario, the RBGPOE is detected as a low-voltage device and may require workarounds, such as forcing PoE-Out or soldering a resistor for auto-on mode.
When used as intended, you don’t need an injector to power one RB5009 from another — you can simply use the PoE-Out of the first RB5009 without any additional injector.
I want to power(~4W) another device from 2nd RB5009, by supplying DC input as RB5009 does not allow poe out when its powered in using PoE.
Still, it would cost (I believe) very little to add on the product page or in an added linked to document a note like:
The RBGPOE is a device intended to be used as power injector, NOT as a power splitter.
It will actually work as a power splitter, but, since it presents a resistance below the one required to be detected as "high voltage" device, the power source (if a Mikrotik PoE out) device will need to be set as "forced on" for it to work correctly or an external resistance needs to be added, otherwise if the power source is set to "auto-on" it won't work correctly and the Mikrotik power source will show the error "Voltage too high".