PoE Static not working

[jknickelbein01]

Hi,

I have a CBS350-24P-4T Business switch and I would like to force the PoE on for connected device, a WAN router, claims it does not comply with IEEE-802.3AT, it can be powered by PoE on pins 4,5 and 6,7 on the RJ45 connector. I see in the manual there is a power inline static command from the CLI which I believe will force the power on, but it refuses to accept this command. I upgraded to the latest release of the software, dated May 2023.

I can change other settings on the port config, but not this. There is nothing on the WebGUI to enable or force the PoE on to supply power to the PoE pins. Is there something I am missing? Can the switch do this? From the outset it looks like it can, but I am not getting it to work.

[Flavio Miranda]

Hi

 What you can do is change the Power mode on the device. This will allow you to set the power limit per port, which should be equivalent to static power.

[jknickelbein01]

Thanks for the info. I tried this, as one of my initial guesses to try get it to work, but alas it didn't work. I have a RUTX11 WAN LTE router that I want to run off PoE. In the manual it says it does not support 802.3AF or 802.3AT because it does not provide PoE power externally. Maybe because of this there is no negotiation for power to the router from the Cisco switch and hence the power is not provided. The RUTX draws up to 16W. I thought this would make a simple architecture and reduced wiring, but I can't find a way to make it work.

[Flavio Miranda]

Does this router supports CDP or LLDP?

Those protocol as usually used for power negotiation

[jknickelbein01]

There is nothing in the manual that indicates it does. That's why I was hoping I could force the power on using the power inline static command.

[Flavio Miranda]

Which model is it?

[jknickelbein01]

We have the CBS350-24P-4T.

[Flavio Miranda]

No, I mean the router

[Flavio Miranda]

 Physically speaking it should work.

[Flavio Miranda]

Yeah, although the 802.3af is available on the switch, they do need to use it. Not all devices support 802.3af but they can negociate the proper power with the switch.

I believe the problem may ne related to the negociation which is done by protocol like  CDP and LLDP.  CDP is cisco standard, so it will not supporte, but LLDP is global standard, it could support.

[jknickelbein01]

I think it's because the 802.3AT standard is not fully supported to negotiate the power on the router. LLDP would be great on the router, but I was hoping I could force the power on to provide the power so I don't require an external power supply. I have tested putting an external power supply onto a PoE adaptor to provide power to the router over the LAN cable which works, but doesn't solve the issue. I hoped the Cisco switch would be able to do that. The whole reason we went for the PoE switch.

Thanks very much for your assistance Flavio.

[Flavio Miranda]

IF you want to go a little bit further you can try to measure the power on the pins with a multimeter and make sure the switch is actually delievering the proper power as it should.

 But, it seems it will not work anyway unfortunatelly.

You are welcome. Good luck.

[KJK99 · Accepted solution]

@jknickelbein01 

I don't think it is going to work. A workaround would be to use a compatible PoE splitter.

[jknickelbein01]

That was my backup solution. I need some for other equipment RS-232 to Ethernet adapters. So I'll get one for this as well.