Pihole DNS issue DNS_PROBE_FINISHED_BAD_CONFIG

[eliza2044]

I have Pihole with wireguard installed on a Google Cloud instance to tunnel my devices' traffic through the tunnel. Wireguard uses Pihole as its DNS. I have been using this setup for probably a year now with no serious issues.

However, since the past Friday, it seems that the pihole DNS does not resolve DNS queries, resulting in a DNS_PROBE_FINISHED_BAD_CONFIG message and as a result no internet. I am sure this is not a wireguard problem as when I switch my configuration file to use a public DNS the internet access is restored.

I have played around trying different things and what seemed to do the trick (temporarily) is running the following sequence of commands.

pihole disable; sudo pihole flush; sudo pihole arpflush; pihole restartdns; pihole enable

Software Versions

• Pi-hole version is v5.17.1 (Latest: v5.17.1)
• FTL version is v5.23 (Latest: v5.23)
• I do not use lighttpd

The issue keeps reoccurring even with this patch and I would really love to get this issue fixed. Does any of you face a similar issue?

Many thanks.

[Bucking_Horn]

@eliza2044

DNS_PROBE_FINISHED_BAD_CONFIG

As that's a browser generated message, it may indicate an issue with the browser's DNS configuration (or that of the system running the browser).

To analyse how DNS and perhaps Pi-hole is involved, run a dig or nslookup for the domain that triggers that browser message from the machine that you expect to use Pi-hole for DNS.

[eliza2044]

Thanks for your response. After digging into the logs I figured out that the DNS I was using on Pihole (Quad9) was not responding after a while. I assume that it was due to the large number of queries.

What's really puzzling though is that when I was running dig or nslookup on domains with Quad9 I was getting responses.

I switched to a different DNS server and everything seems to be back to normal now. It was something I couldn't predict as it used to be working fine up until a moment.