06-26-2020 01:56 AM
Hi,
I wonder if it's normal for the PoE voltage be very fluctuating?
I have seen voltages from as low as 31V all the way up to 94V
Mainly I monitor the switch via SNMP using Observium, but I have also observed strange voltags using CLI command:
show power inline consumption
06-26-2020 10:03 AM
- Make sure to use latest firmware
M.
06-28-2020 02:56 AM - edited 06-28-2020 02:57 AM
As far as I know I'm running latest version, both boot version and FW version. Here you can see what versions I'm running:
06-28-2020 04:17 AM
Hmmm perhaps an indication the power supply has seen some days and might need to be replaced? I wouldn't wanna jump to conclusions, but if its been installed and running constantly, that might be it. They wear down over time.
In my days as a data center tech power supplies and mechanical drives were the most often replaced FRUs. Not sure which was top dog... but those 2 parts waaay exceed any other component in replacements. There was a period of time that GBICs were getting replaced like crazy but I think there was a bad batch or something.
Anywasy, I'm only speculating. Unfortunately I know thatthe PSes on thes are not quick or hot-swap. That is unless the 52P is different that the 28Ps that I have. I mean yea the pull more power.. so maybe they are. I haven't seen on up close in ages.
I wanted to thank youfor your post becauses I had recently updated my fw on the 28P but I didn't realize there was a newer boot version. So I just looked through all the releases and found the 1.4.1.0.3 that gave me the same Boot version you have. I was so focused on all the incremental upgrading and was having issues with TFTP that I completely overlooked this one.
I'll keep an eye on this post. I'm curious as to what the answer to your power fluctuations is. Later!
06-28-2020 06:49 AM
So you're speculating that what you're seeing may be normal beahviour? Given that way that PoE is so variable that may be true. Some switches boast about how they can essentially control the voltage and current very tightly to conserve and provide power to more devices concurrently than it appears they should based on specs.
I honestly haven't paid close enough attention in practice to know. I do have a copy of the 802.3bt spec from IEEE. I have read through it but not to a critical level. Seems like a bit of research into that idea would be worthwhile. Either to confirm or rule that out as acceptable, within-spec, operating as designed beaviour.
06-28-2020 06:56 AM
Perhaps is has to do with the particular cabling. The grade, the type (stranded vs solid core), shielded vs non-shielded, category, length, wear or stretching, quality of terminations, etc. There are so many potential factors.
Are you seeing this remotely or do you have access to the switch physically? Just curious as to whether its happening on certain ports and if there's anything obviously different about the cabling.
It's not my intention to confuse the issue, I just started looking at the IEEE 802.3bt spec and this occurred to me.
06-28-2020 11:27 PM
Yes, of corse it could be the power supply.
But I also want to add that prior to SG500-52P I used a smaller cusin SG200-26P, and it showed the exact same fluctuating PoE voltage.
Also, the only thing connected to the switch that's using PoE is a Ubuquiti Unifi AP AC Lite, which draws about 4W, and I'm thinking that the readings aren't very accurate such small load?
I manly use Observium to monitor the switch via SNMP, but I have also seen strange voltages using the CLI command "show power inline consumption"
The AP connected to the switch using a 3m Cat5e cable.
Btw, have you ever checked the PoE voltage of your SG500-28P switches?
06-29-2020 12:36 AM
06-29-2020 01:48 AM
I am not seeing any real issues with this, both the switch and the connected AP runs ust fine, I just feel that it can't be good for the AP to get such wide variation in the input voltage.
I have also thought about measuring the actual voltage, but it's also a bit hard to do when the AP is connected using a patch cable connected directly to the switch, I'll try to connect it via a wall jack and measure the voltage on the krone connector.
Here are some log from Observium:
https://i.imgur.com/rMQd9wg.png
06-29-2020 02:20 AM
06-29-2020 01:57 AM
06-29-2020 02:39 AM
This is what the output of "show green-ethernet" looks like:
https://pastebin.com/raw/bTcq33Wd
And this is what the output of "show eee" looks like:
06-29-2020 04:29 AM
06-28-2020 01:20 PM
Perhaps is has to do with the particular cabling. The grade, the type (stranded vs solid core), shielded vs non-shielded, category, length, wear or stretching, quality of terminations, etc. There are so many potential factors.
Are you seeing this remotely or do you have access to the switch physically? Just curious as to whether its happening on certain ports and if there's anything obviously different about the cabling.
It's not my intention to confuse the issue, I just started looking at the IEEE 802.3bt spec and this occurred to me.
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