DNS N/A and SERVFAIL responses after updating LAN switch

Expected Behaviour:

Successful DNS lookups after firmware upgrade on Unifi switch.

Actual Behaviour:

The last 2 firmware upgrades have resulted in a flurry of "N/A" and "SERVFAIL" responses on all DNS queries until I reboot my Raspberry Pi running Pihole 5.18.2 with Unbound.

Some examples:

OK (sent to 192.168.20.1#53)	N/A
OK (answered by 127.0.0.1#5335)	SERVFAIL (0.8ms)

I'm just trying to understand what happened, I truly doubt this is a Pihole issue.

What happened/changed was that on my Unifi network setup with UDM-SE gateway/router/firewall and USE-16-PoE switch, I ran a firmware upgrade yesterday on the switch. After it finished, the switch restarted. When it came back up at about 11:18am CDT, all devices were visible on my network but started showing DNS lookup problems. That's when it looks like the errors started in my Pihole. Note to self, stop upgrading network devices from a remote location! :slight_smile:

I was able to physically access the RPi around 4:30pm CDT, and was able to get into the Pihole web interface via IP (URL would not work), saw the errors in the log and restarted via Settings/Restart System. After the RPi restart, everything was working again as expected.

The same thing, as I recall, happened the last time up upgraded the switch firmware, but that is the first time I remember that ever happening. I've run other updates on the switch before then with no issue over the last 12 - 18 months.

Does anyone have any thoughts as to what's happening here? Is there another was to correct this besides restarting the RPi? Or maybe I should just expect this with my hardware setup, not sure.

Debug Token:

waqkRLYz

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