Failed to send UDP request (Network Unreachable)

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1

Expected Behaviour:

Raspberry Pi 5

Debian GNU/ Linux 12 (Bookworm)

Actual Behaviour:

getting error that states it failed to send UDP request, network unreachable

Debug Token:

Https://tricorder.pi-hole.net/kkf7na46/

2

Your debug log shows that you've configured your Pi-hole to use a public DNS server IPv6 as upstream, but your network (or at least your machine hosting Pi-hole) does not have public IPv6 connectivity:

   [dns]
     upstreams = [
       "8.8.8.8",
       "8.8.4.4",
       "2001:4860:4860:0:0:0:0:8888",
       "2001:4860:4860:0:0:0:0:8844"
     ] ### CHANGED, default = []

*** [ DIAGNOSING ]: Network interfaces and addresses
(…)
   2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
       link/ether <redacted> brd ff:ff:ff:ff:ff:ff
       inet 192.168.0.3/24 brd 192.168.0.255 scope global noprefixroute eth0
          valid_lft forever preferred_lft forever
       inet6 fd80:<redacted>2e/64 scope global dynamic noprefixroute 
          valid_lft 1779sec preferred_lft 1779sec
       inet6 fe80::<redacted>70/64 scope link noprefixroute 
          valid_lft forever preferred_lft forever

Hence, it can't connect to public IPv6 addresses (range 2000::/3), which triggers the Network Unreachable warning.

To get rid of those warnings, untick Google's IPv6 DNS servers from your Pi-hole's upstreams.