Root cause of Uptime Kuma DNS up/down alerts: Pi-hole's upstream config
included Google IPv6 DNS (2001:4860:4860::8888), but netinfra-01 has no
IPv6 internet route. Every forwarded query to the IPv6 upstream failed
with "Network unreachable", causing intermittent DNS resolution
failures every ~8 seconds.
Fix applied to both netinfra-01 and netinfra-02:
- Pi-hole upstream set to 8.8.8.8 only (IPv4); removed 192.168.3.16
(retired netboot) and 2001:4860:4860::8888 (IPv6 Google DNS)
- IPv6 disabled at kernel level (/etc/sysctl.d/99-disable-ipv6.conf)
- knel.net authoritative resolution unchanged (Technitium via revServers)
Verified: zero IPv6 warnings, zero connection errors, DNS resolving
cleanly from all paths after fix.
[#376]
mrcharles
4f82520e0e