Switch rebooting and disabling PoE

[colinhowlin]

We've noticed an issue on some of our switches which are powering up Cambium ePMP radios.
If a switch loses power, due to power outage or similar, upon reboot it will detect a link on a port, disable PoE, reboot and then detect a link on the next port and reboot again.
This continues through all ports - disabling PoE and rebooting switch.
Only on ports with ePMP radios. On ports with Ubnt or PMP450 we do not have this issue.

This is quite a problem as it means we have to manually disable PoE on all ports and then turn it back on one by one.
Sometimes, if we enable PoE on all ports it will start the process all over again.
Have tried disabling PoE Smart but this doesn't resolve issue either.

Has anyone else noticed this issue or similar?

[sirhc]

And what firmware version are you running?

[colinhowlin]

We were seeing this on 1.3.8 and 1.3.9.
Both switches have now been upgraded to 1.4.2 FINAL.
Will have to wait and see if issue arises again - have had a few outages due to weather lately so might be another sooner than later.

I didn't see anything in change logs - was there an issue identified?

[nickwhite]

I have noticed a similar issue on one of our switches, running 1.4.1. Happening for the last month or so. It did this randomly about 6-7 months ago on 1.3.8 and 1.3.9, but seemed fine up until recently. The switch has been rebooting once or twice a day on average. And when it comes back up, about half the time it will detect link on a port and not turn on POE. The port that it chooses not to turn on seems random, but has always been a 24V. It was powering a Mikrotik router, so this caused some routing issues for us, so we moved it to a power adapter about 2 weeks ago. Since then, it has been a random AP port. This is a WS-10-250-AC and is only powering 4 devices currently.

[sirhc]

I have noticed a similar issue on one of our switches, running 1.4.1. Happening for the last month or so. It did this randomly about 6-7 months ago on 1.3.8 and 1.3.9, but seemed fine up until recently. The switch has been rebooting once or twice a day on average. And when it comes back up, about half the time it will detect link on a port and not turn on POE. The port that it chooses not to turn on seems random, but has always been a 24V. It was powering a Mikrotik router, so this caused some routing issues for us, so we moved it to a power adapter about 2 weeks ago. Since then, it has been a random AP port. This is a WS-10-250-AC and is only powering 4 devices currently.

OK first off switches should NOT just reboot and if it is there is something terribly wrong.

If your switch is rebooting you may be experiencing a Ground Potential shift that is causing this and I would not be surprised if your switch has not taken damage to the current sensors or worse.

Here are some good posts on grounding:
viewtopic.php?f=30&t=1816 <== THIS IS A RECENTLY ADDED NEW POST ON GROUNDING ISSUES
viewtopic.php?f=30&t=188
viewtopic.php?f=30&t=1429

I would check all your current readings on the main status tab and make sure they look right. Smaller ground potential shifts seem to damage the current sensors first from what we see with RMAs but massive shifts go after everything. We are working on trying to improve the resilience of the current sensors and made changes to Rev F boards to "try" and combat this problem which would not be a problem with proper grounding practices. It will take a year of comparing RMA damaged boards to the previous year to see if the changes made any difference.

[colinhowlin]

Just to clarify, the switches we were seeing this on weren't rebooting at random.
If they were powered off for a time, due to power outage, upon restoration of power we would see it reboot and cycle through the ports disabling PoE.
Again, only on Cambium ePMP radios which we had powered up at 48V.
Error in log was not the '...power should not be 0.' error, instead it was I think 'Link detected on port 1- disabling PoE'.

[sirhc]

Just to clarify, the switches we were seeing this on weren't rebooting at random.
If they were powered off for a time, due to power outage, upon restoration of power we would see it reboot and cycle through the ports disabling PoE.
Again, only on Cambium ePMP radios which we had powered up at 48V.
Error in log was not the '...power should not be 0.' error, instead it was I think 'Link detected on port 1- disabling PoE'.

Well if your current sensors are not damaged and this is happening and you are running an older version of firmware there was several bugs awhile back that did this, what firmware are you running?

[colinhowlin]

This was happening on switches running 1.3.8 and 1.3.9.
We have upgraded to 1.4.2 but have not had any power issues since so it has not arisen again.

Will update if it does happen again - if not, will take it that it was the f/w.

Thanks
Colin