Using pi-hole as DHCP server, pi.hole sometimes does not resolve

[ksylvan]

Hi everyone,

I have an RPi3 running Raspberry Pi OS (latest Debian) and latest pihole, running on my local network as the DHCP server and DNS server.

Previously my AT&T uVerse ARRIS BGW210-700 router was the DHCP server.

Expected Behaviour:

Putting in “pi.hole” into browsers should resolve to the local address.

uname -a
Linux raspberrypi 5.4.51-v7+ #1333 SMP Mon Aug 10 16:45:19 BST 2020 armv7l GNU/Linux

pi@raspberrypi:~ $ cat /etc/debian_version 
10.4

pi@raspberrypi:~ $ pihole version
  Pi-hole version is v5.1.2 (Latest: v5.1.2)
  AdminLTE version is v5.1.1 (Latest: v5.1.1)
  FTL version is v5.2 (Latest: v5.2) 

Actual Behaviour:

The following page comes up on some clients (iPhone, other devices)

http://dnserrorassist.att.net/search/?q=http%3A//pi.hole/&r=&t=0&bc=

Debug Token:

https://tricorder.pi-hole.net/sfl23ymo3p

[ksylvan]

SOLVED

TL;DR

Needed to set correct ipv6 static address and fix stupid AT&T and router settings.

Details

1. Look at output of ip -6 -a show eth0 and picked the 2600: address (with “/64 scope global”)

2. Replace the ipv6 addresses in both setupVars.conf and local.list in /etc/pihole

3. Use the info in this gist to OPT OUT of the AT&T DNS Assist nonsense!

4. Make sure that the ipv6 DHCP prefix delegation stuff was set in the ARRIS BGW210-700 router.

After all of that was set, disconnected and reconnected the clients and verified that the ipv6 address for the pi-hole was automatically showing up in the DNS servers.