Running on a Raspberry 4+, OS Raspbian GNU/Linux 11 (bullseye)
Actual Behaviour:
I am facing problems with DNS resolution that stopps for 2-3 minutes and then continues working normally. This happens 1-2 times a day. While that time I can see these information in the logs:
WARNING in dnsmasq core: Maximum number of concurrent DNS queries reached (max: 150) in pihile-FTL.log
as well as
dnsmasq[27562]: config error is REFUSED in pihole.log
This line is shown at the same time for almost each query log line.
These indicate that your upstream DNS server is not responding:
The configured maximum number of concurrent DNS queries for a given server is reached. The system is either very busy at the moment or not receiving queries from the configured upstream. Check your connectivity or the upstream DNS server status.
The warning can also be printed when being spammed with an excessive amount of duplicates or when the upstream server never replies for specific domains. Check your logs and try to identify similarities between the query directly preceding this warning and earlier queries in /var/log/pihole.log . Try to find out if your upstream does maybe never reply to specific domains and fix this.
This warning is printed at most once every five seconds (per upstream server) to help mitigate unlimited log file growth.
As a first step, change your upstream DNS server from unbound to something else and see if the problem resolves. You don't need to uninstall or stop unbound, just don't use it for a bit.
Many thanks. I already checked this and also with other upstream DNS servers it seems to be the same. Another thing that comes into my mind is that the problem could be related to the internet connection itself or would the error indication be different in that case? What I know for sure, is that the router does not report any disonnect or error while that.
Regards,
Torsten