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Jobius
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RB5009UPr+S+ poe-out status: no_valid_psu with PoE in power only

Tue Sep 06, 2022 11:56 pm

We're trying to power a Wireless Wire radio from a new RB5009 running RouterOS 7.5 while powering the 5009 with PoE. No power is delivered to the radio, and the comment field on all interfaces when we try is "poe-out status: no_valid_psu". As soon as we plug in to the power jack on the 5009, it works. Is this normal? Shouldn't we be able to send the PoE in voltage to PoE out ports?
 
mkx
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Re: RB5009UPr+S+ poe-out status: no_valid_psu with PoE in power only

Wed Sep 07, 2022 7:17 am

Standard PoE 802.3 af/at provides between 15W (af) and 30W (at) - both at power sourcing equipment, substract power losses on cable. Given that rated power consumption of device itself is 15W, there's not much that is left for attached devices, is there? Tgere's 802.3bt standard which specifies up to 100W but MT doesn't support it.
 
Jobius
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Re: RB5009UPr+S+ poe-out status: no_valid_psu with PoE in power only

Wed Sep 07, 2022 7:01 pm

The LHG 60G dish we were trying to power typically draws about 5 watts. We tried several different PoE sources, any of which could provide plenty of power for the switch and the radio, and we tried connecting more than one at the same time. I don't think the problem is capacity, it's that the switch doesn't try to power anything but itself from PoE in. To get PoE out, we had to connect DC to the barrel connector.

Is that really how it's supposed to work?
 
mkx
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Re: RB5009UPr+S+ poe-out status: no_valid_psu with PoE in power only

Wed Sep 07, 2022 7:13 pm

IMO that's the way it's supposed to work.

PSE (device which provides power) doesn't know how much power will PD (powered device) draw until after handshake finishes. So if PSE doesn't clearly have power budget to provide full capacity (802.3 at means 30W output from PoE port), it's logical (to me) that it doesn't even start the negotiation. Surely if PSE has multiple PoE out ports, it can do some power budget overbooking and in case power draw exceeds capacity, it disconnects power to select PDs (in order of priority). I don't think you would like to see that too often. With PoE in, device knows very well it's power budget: 25W less own consumption (up to 15W). With DC jack or 2-pin terminal device doesn't know power budget so it has to assume power available is ample enough for PoE out.

Next tricky thing might be PD negotiation ... PD should properly "signal" own power requirements ... however classification is optional and default is Class 0 with 15W power budget. Not sure if Mikrotik devices properly implement classicifation (I wouldn't be much surprised if they didn't). If PoE in power budget is 25W, own power consumption is 15W (it has to assume maximum consumption to avoid any instabilities), then remaining 10W is clearly not enough to power Class 0 PD with 15W power draw.
 
ToTheCLI
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Re: RB5009UPr+S+ poe-out status: no_valid_psu with PoE in power only

Thu Sep 08, 2022 2:45 pm

We're trying to power a Wireless Wire radio from a new RB5009 running RouterOS 7.5 while powering the 5009 with PoE. No power is delivered to the radio, and the comment field on all interfaces when we try is "poe-out status: no_valid_psu". As soon as we plug in to the power jack on the 5009, it works. Is this normal? Shouldn't we be able to send the PoE in voltage to PoE out ports?
Did you use a crossover cable to power the RB5009 or a regular ethernet cable?
 
Jobius
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Re: RB5009UPr+S+ poe-out status: no_valid_psu with PoE in power only

Thu Sep 08, 2022 7:27 pm

Did you use a crossover cable to power the RB5009 or a regular ethernet cable?
Regular ethernet cable from PoE injector rated 55V at 0.6A; switch reports poe-in-voltage 56.1V. We'll probably use a diode to pull the power off the ethernet and send it to the DC jack or 2-pin connector. It would have been nice to avoid that.

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