So I had an outage of my internet today that resulted in my internet dropping for 4 hours. Upon the upstream network reconnecting there was no network DNS resolution. Devices using hard coded Google DNS at 8.8.8.8 like Google Home devices worked fine.
After pulling a debug log I rebooted the PiHole and it came back on line and served DNS as expected.
Network config:
PiHole -> Untangle Firewall (with DHCP Server) -> Archer Modem -> NBN Onramp
The Untangle firewall has PiHole set as DNS Server in the DHCP server it provides to the network.
Only the upstream NBN internet failed with DHCP leases still being handed out by Untangle appliance correctly.
I just want to understand why this is happening as we often get outages of our upstream network due to maintenance and every time I see the same where the PiHole will go offline after a few hours.
Todays outage started at 8.30am with the logs in the PiHole stopping at around 10am. I was not home during the day, but the kids got home around 3pm and reported no internet access.
Before I restarted the PiHole I was seeing errors like the following in the PiHole GUI:
PHP error (2): fsockopen(): unable to connect to 127.0.0.1:4711 (Connection refused) in /var/www/html/admin/scripts/pi-hole/php/FTL.php:47
Expected Behaviour:
After internet outage is restored PiHole should correctly handle DNS for network.
Actual Behaviour:
Devices using PiHole for DNS will not resolve addresses until the PiHole is rebooted. PiHole can be reached by Browser on its IP address so it is still running the WebGUI at least.