LE: By following this link I was able to replace my second DNS (the one that is not accessible through the router's interface) with the Cloudflare one (just so that I have a backup in case something goes terrible wrong with my PiHole).
This morning I didn't find any diagnostic messages, but I've found that the DNS was down since yesterday. Basically I've had a hole from midnight until this morning when PiHole didn't worked at all.
I solved it with restartdns without issues:
$ pihole restartdns
[sudo] password for iosif:
[✓] Restarting DNS server
$
@Bucking_Horn I believe that now I have an IPv6 issue on my hands. I did a test on https://www.test-ipv6.ro/ and I got a red message saying "Our tests show that you will have a broken or misconfigured IPv6 setup, and this will cause problems as web sites enable IPv6."
Your current telnet API stats look normal.
Did you perhaps run those after clearing your pihole-FTL.db?
They wouldn't contain the potentially offending domains and clients then.
Your zgrep results show that your router's excessive requests for its own name seem to have ceased after about February 21st, which could be about the time when you've disabled CF.
This would still allow your clients to by-pass your Pi-hole (via Cloudflare this time).
As mentioned:
Ok, let's take it one step at a time.
Yes, my router stopped being chatty since I disabled CF and yes, I cleared the FRL.db that day due to space issues. So now I have fresh stuff there.
I replaced the second DNS server on my router with Cloudflare (instead of the router's IP address) thinking that this should provide me with a backup solution in case PiHole stops working (for various reasons). Like for example yesterday morning Pihole stopped working although the VM was ok (restartdns solved the issue).
The idea is that in case PiHole misbehaves I do not want for my entire network to have issues until I fix it (my wife and daughter would kill me).
What about IPv6? I tried to follow all the guides and post I've found on this topic but I still can't seem to find the culprit. Must be something between my Router and PiHole or a little bit on both.
Many thanks for your help.
That may be sound while you sort your issues.
Just keep in mind that it is not a backup - your clients are free to pick any DNS server they are aware of for any individual DNS request at their own discretion. Pi-hole will be by-passed if it isn't the only DNS server.
In that case, it may be better to continue this as a separate topic, so we could mark this one as solved.
Your public IPv6 connectivity would be outside of Pi-hole's scope.
Pi-hole could be only involved here if it would block any domains that the tesing website would try to access, in which case How do I determine what domain an ad is coming from? could help to identify those domains.
For the moment everything seems stable enough with my little PiHole VM. Hence, I marked your post with "Disable CF" as the Solution.
Any chance there is a workaround for that CF? I keep forgetting which IP is for each host when I look through the Dashboard.
Many thanks.