I am sorry if this is duplicate, but I didn't find any issues that match mine. I just got started with my HomeLab and Pi-Hole is the first service I installed.
There should be no connection issues.
Getting these errors once in a while:
Connection error (9.9.9.9#53): TCP connection failed (Host is unreachable)
The debug log shows that there is connectivity to an IPv4 server at least once:
*** [ DIAGNOSING ]: Name resolution (IPv4) using a random blocked domain and a known ad-serving domain
[✓] fghdsj.com is NOERROR on lo (127.0.0.1)
[✓] fghdsj.com is NOERROR on eth0 (192.168.0.195)
[✓] doubleclick.com is 142.251.41.174 via a remote, public DNS server (8.8.8.8)
You're running in a docker container and that's going to eliminate the possibility of IPv6:
*** [ DIAGNOSING ]: Name resolution (IPv6) using a random blocked domain and a known ad-serving domain
[✓] bottlehere.com is NOERROR on lo (::1)
[✓] No IPv6 address available on eth0
[✗] Failed to resolve doubleclick.com via a remote, public DNS server (2001:4860:4860::8888)
So take out all of the IPv6 upstreams that you have, you can't use them:
2026-04-29 16:29:22.875 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
2026-04-29 16:30:02.829 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
2026-04-29 16:32:32.633 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
2026-04-29 16:33:57.487 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
2026-04-29 16:34:53.637 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
2026-04-29 16:35:38.711 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
2026-04-29 16:35:59.881 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
2026-04-29 16:36:23.572 UTC [53M] WARNING: Connection error (2620:fe::fe#53): failed to send UDP request (Network unreachable)
There's some kind of intermittent networking issue from Pi-hole to the upstreams, these errors are a combination of DNS queries getting out to the upstream but not getting a reply and then not even being able to send queries at all.
2026-04-29 16:25:54.014 UTC [27097/F53] WARNING: Connection error (149.112.112.11#53): TCP connection failed while receiving payload length from upstream (Host is unreachable)
2026-04-29 16:25:54.014 UTC [27079/F53] WARNING: Connection error (149.112.112.11#53): TCP connection failed while receiving payload length from upstream (Host is unreachable)
2026-04-29 16:25:54.015 UTC [27099/F53] WARNING: Connection error (149.112.112.11#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:54.016 UTC [27096/F53] WARNING: Connection error (149.112.112.11#53): TCP connection failed while receiving payload length from upstream (Host is unreachable)
2026-04-29 16:25:57.023 UTC [27111/F53] WARNING: Connection error (9.9.9.9#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.023 UTC [27110/F53] WARNING: Connection error (9.9.9.9#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.023 UTC [27103/F53] WARNING: Connection error (9.9.9.11#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.026 UTC [27107/F53] WARNING: Connection error (149.112.112.112#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.026 UTC [27105/F53] WARNING: Connection error (149.112.112.112#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.026 UTC [27101/F53] WARNING: Connection error (9.9.9.11#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.028 UTC [27098/F53] WARNING: Connection error (149.112.112.11#53): TCP connection failed while receiving payload length from upstream (Host is unreachable)
2026-04-29 16:25:57.028 UTC [27106/F53] WARNING: Connection error (149.112.112.112#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.028 UTC [27102/F53] WARNING: Connection error (9.9.9.11#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.028 UTC [27108/F53] WARNING: Connection error (9.9.9.9#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.030 UTC [27100/F53] WARNING: Connection error (9.9.9.11#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.030 UTC [27109/F53] WARNING: Connection error (9.9.9.9#53): TCP connection failed (Host is unreachable)
2026-04-29 16:25:57.030 UTC [27104/F53] WARNING: Connection error (149.112.112.112#53): TCP connection failed (Host is unreachable)
Sometimes DNS resolution does work so it's not a constant issue:
Apr 29 16:36:36 dnsmasq[53]: forwarded <REDACT> to 9.9.9.9
Apr 29 16:36:36 dnsmasq[53]: reply <REDACT> is <CNAME>
Apr 29 16:36:36 dnsmasq[53]: reply <REDACT> is <CNAME>
Thank you!