POE Switch Problem, Turning off with another switch connected?

Gillbot

Gillbot

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Network layout is:
Cable Modem -> GigaPlus GP 525 0802 (& Wired Devices) -> TrendNet TPE TG380 (& POE Devices)

Noticed the other day there was no WiFi so I checked the network, my controller and AP's were all offline. No power on the POE switch. Flipped the power switch off then on, nothing. Pulled the power cord and it shows voltage so I plugged it back in. Flipped the power switch on and off again, nothing. Assumed the switch was dead so I drug out a Netgear Gigabit POE I have and plugged it in, all good and everything was back online.

Plugged in the TrendNet on my desk and powered right up fine. WTF? Pulled the Netgear and put back the TrendNet and nope, no power. Unplugged everything again and powered up the switch fine. So I started plugging network cables in one at a time, the GigaPlus was causing it to power off. This entire setup has been running for quite some time so this is new. I've googled a bit and most complaints for POE switches powering down seem to stem from motherboard NICs and certain power settings in BIOS but i've seen nothing about another switch. I moved some cables around and am currently up and running using one of the SFP ports connected to the GigaPlus but would love to figure out this issue.
 
Can you plug the GigaPlus into a non PoE port on your TrendNet, or disable PoE on said port in the trendnet if it has a management interface?
 
There are no non-POE ports and the switch is not managed. I tried switching to a couple other ports and get the same power off result. It is back up using one of the SFP ports but those aren't 100% reliable for me so i'd prefer not to use this "fix" long term. Normally I keep my work PC plugged in on the SFP since that system doesn't need 100% uptime, but having an entire branch of my network on SPF doesn't sit well.
 
Strange issue. Any 'updates' on either the gigaplus or the trendnet? One experiment I would try is putting a dumb switch in between the gigaplus and the trendnet and see if that fixes the problem (my hunch is that it will), which means it's simply something not talking correctly anymore between the two.
 
They are both dumb switches so there's nothing to update. My next plan was to do just that with a dumb switch but figured hooking into the SFP port was similar and that did work.
 
when you are hooking into the SFP port are you using SFP RJ45 adapter or doing a DAC?

I am thinking similar, the giga does not like the PoE port and thus is dropping the link because it should not be getting power over said link...
 
Yes, 2.5GBE SFP to RJ45. Something has to have changed recently though as it's been working like a charm for well over a year, then all of a sudden they just decided not to get along anymore.
 
I had a cheapo POE switch die on me where if you plugged anything in to a certain bank of ports, it created a short and powered the unit off. I also had a POE switch go bad where it would cause traffic loops inside the switch. Wireshark would tell me loops were detected when there physically wasn't one. Removed cables from switch and it went away. For a sudden die of a known working setup, my best unhelpful to you guess is the POE switch has a bad solder joint or other POE heat/wear defect. Assuming you tried a different port on the Giga as well as a new cable, thats the only logical deduction I can come up with.
 
Nobu said:
No chance you are overloading the power supply for that switch?
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It’s powering 4 devices so I doubt it. I’m of the opinion that the cheapo gigaplus is confusing the Poe when it tries to determine if power is needed. Or as others have said, the Poe is just going bad.

Edit: I need to dig out another 2.5gb switch and see, I think I have one but the better question is where did I put it.
 
Nobu said:
No chance you are overloading the power supply for that switch?
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This is a good thing to check as a power supply that has become marginal with time might do this. I'd check this on both switches. In fact, I think this has got to be it since everything else has stayed the same.
 
Servethehome says the gigaplus has about 130W budget for it's 8 ports. That's about 32W each if you use only 4 ports, but keep in mind long eth runs and damaged/low quality cables can increase the effective demand on the ports. And if you are chaining PoE switches, that will put a heavy load on the port powering that switch and PoE devices on that switch.
 
Gillbot said:
It’s powering 4 devices so I doubt it. I’m of the opinion that the cheapo gigaplus is confusing the Poe when it tries to determine if power is needed. Or as others have said, the Poe is just going bad.

Edit: I need to dig out another 2.5gb switch and see, I think I have one but the better question is where did I put it.
Click to expand...

If you've isolated it to the gigaplus, did you try using a different port with that? Maybe the gigaplus's magnetics have degraded and now it will sink current, and that trips protection on your TrendNet.
 
SamirD said:
This is a good thing to check as a power supply that has become marginal with time might do this. I'd check this on both switches. In fact, I think this has got to be it since everything else has stayed the same.
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I have two AP’s and one IP phone on it, plus one non-Poe device. I can’t see it being anywhere near overloaded. I thought it was powering 4 devices but it isn’t. I just initially ran out of ports on the gigaplus so I ran a line to another switch across the house with a port on the trend net.
Nobu said:
Servethehome says the gigaplus has about 130W budget for its 8 ports. That's about 32W each if you use only 4 ports, but keep in mind long eth runs and damaged/low quality cables can increase the effective demand on the ports. And if you are chaining PoE switches, that will put a heavy load on the port powering that switch and PoE devices on that switch.
Click to expand...
Two of the runs are 6ft cat 6 cables and the other is a maybe 25ft cat 6 to the other AP. The 4th is a short cat6 cable to the gigaplus. Can’t say they are good cables or not, just bought from mono price and never gave any issues otherwise. I have tried swapping them out to others I have non-mono price but same results. Thus far it doesn’t seem to be a cable issue directly.
toast0 said:
If you've isolated it to the gigaplus, did you try using a different port with that? Maybe the gigaplus's magnetics have degraded and now it will sink current, and that trips protection on your TrendNet.
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I’ve tried swapping all over with ports and cables, same problem no matter what. It’s the gigaplus itself that’s the issue. I can’t move devices from the gigaplus over to the trend net and everything is fine, but the moment that switch gets plugged in, boom, lights out. I’m leaning more towards the cheap gigaplus being the culprit but I plan to pop the tenda in place. I just need to do it early in the morning so I don’t hear two teenagers and a wife complain about no internet. But it’s alive for now using the sfp ports so I haven’t messed with it.
 
Gillbot said:
Yes, 2.5GBE SFP to RJ45. Something has to have changed recently though as it's been working like a charm for well over a year, then all of a sudden they just decided not to get along anymore.
Click to expand...
Could be damage from heat over time since the SFP to RJ45 modules tend to run hot....
 
Gillbot said:
I have two AP’s and one IP phone on it, plus one non-Poe device. I can’t see it being anywhere near overloaded. I thought it was powering 4 devices but it isn’t. I just initially ran out of ports on the gigaplus so I ran a line to another switch across the house with a port on the trend net.
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Not necessarily overloading, but a power supply can change voltage or ampage or both and then you have odd stuff like this. If you've got something else that can power it for a test, that's what I'd try. I'd even go so far as getting a new power supply and trying it.
 
SamirD said:
Not necessarily overloading, but a power supply can change voltage or ampage or both and then you have odd stuff like this. If you've got something else that can power it for a test, that's what I'd try. I'd even go so far as getting a new power supply and trying it.
Click to expand...
I believe I have a power supply tester somewhere for work to do stuff like this, if I can locate it I may try to test it with that.
 
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