Clients can only access internet with DNS manually set to PiHole

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1

Expected Behavior:

Pi-Hole: v6.1.4
Raspberry Pi OS: 6.12.47
Spectrum Router Model: SAX1V1K

Pi-hole running, Router DNS set to PI-hole IP, should be able to connect to internet while clients automatically get DNS server from router.

Actual Behavior:

Clients can’t connect to outside internet unless DNS server manually set.

Debug Token:

Receive error when uploading log:

Error message: curl: (6) Could not resolve host: tricorder.pi-hole.net

Attached the log to the post

[[Debug log redacted for privacy.]]

2

Both Ethernet and Wifi interfaces are connected on the Pi.
I would recommend disconnecting one of them for diagnosing.

Also you have below in the debug log:

2025-10-23 17:43:15.884 UTC [940/T1082] INFO: Local time is too inaccurate, retrying in 600 seconds before launching NTP server

Check if date/time on the Pi is not too far off and if its "synchronized" with below :

timedatectl

For syncing details:

timedatectl timesync-status

3

I will attempt to fix the timing.

For the ethernet + wifi, my spectrum router requires a primary and secondary DNS server and that was one of the solutions I came across. Along with setting the secondary DNS to an unused IP address on the network. I’ll turn off wifi on the rpi so that its IP is ‘unused’

4

timedatectl output:

           Local time: Sat 2025-10-25 11:06:12 UTC
       Universal time: Sat 2025-10-25 11:06:12 UTC
             RTC time: n/a
            Time zone: UTC (UTC, +0000)
System clock synchronized: yes
NTP service: active
RTC in local TZ: no

timedatectl timesync-status output:

Poll interval: 34min 8s (min: 32s; max 34min 8s)
Leap: normal
Version: 4
Stratum: 3
Reference: 52441E23
Precision: 1us (-23)
Root distance: 51.643ms (max: 5s)
Offset: +2.037ms
Delay: 52.693ms
Jitter: 6.409ms
Packet count: 78
Frequency: -7.806ppm

5

Here is a new debug log:
https://tricorder.pi-hole.net/rJcs18il/

6

Here is another debug after setting router DNS to PiHole DNS for dns 1 and unused ip as dns 2.
https://tricorder.pi-hole.net/IAlaeuzT/

Android phone giving ‘No internet’ on the wifi while router is configured to use the pihole. I did notice that the DNS server address on the phone was an ipv6 address, so will be looking to see if that’s causing an issue.

7

Before altering any router settings, first check if Pi-hole responds via IPv4 by running below two on a Windows, MacOS or Linux client (with 10.0.0.2 being my Pi-hole instance):

C:\>nslookup pi.hole 10.0.0.2
Server:  ph6a.home.dehakkelaar.nl
Address:  10.0.0.2

Name:    pi.hole.home.dehakkelaar.nl
Addresses:  fe80::XXX
          10.0.0.2

C:\>nslookup pi-hole.net 10.0.0.2
Server:  ph6a.home.dehakkelaar.nl
Address:  10.0.0.2

Non-authoritative answer:
Name:    pi-hole.net
Address:  162.244.93.14

If that works, next you have to make sure your router doesnt advertise any IPv6 DNS servers to the clients via IPv6 RA (Router Advertisement) or via DHCPv6 that would allow the clients to bypass Pi-hole.
DHCPv6 should be disabled anyway on the router bc it isnt supported on a bunch of OS'es.
You can check for any RDNSS (Recursive DNS Server) addresses advertised via IPv6 RA if run below on the Pi.
Below will broadcast an IPv4 DHCPDISCOVER plus an IPv6 RA solicitation and catches the response from the router(s):

sudo pihole-FTL dhcp-discover

Dont post unredacted output for above one here for privacy!
Below an example of IPv6 RDNSS addresses advertised via IPv6 RA:

EDIT: Ps, is below fixed now?