Router making thousands of PTR queries back to Pi-Hole

[deHakkelaar]

@rubinho

I have set the DNS Server back to Auto in Basic: Network

In Advanced|DHCP/DNS I have added

dhcp-option=6,192.168.1.2

Above is the correct way if can make it work this way.
You have to make it so that the router advertises the Pi-hole IP as the only dns-server when run below one:

pi@ph5b:~ $ pihole-FTL dhcp-discover
Scanning all your interfaces for DHCP servers
[..]
   dns-server: 10.0.0.2
[..]

If you cant make it work this way, you could opt to enable Pi-hole's own DHCPv4 service and disable the one on your router:

How do I use Pi-hole's built in DHCP server (and why would I want to)?

Using Your Existing Router For Network-wide Ad Blocking You might not need to use Pi-hole's DHCP server: In many home environments, your router also functions as your DHCP server. In this case, you can often set Pi-hole to be the DNS server for your network clients in the router's DHCP (or LAN) settings page, which allows all of your network clients to block ads simply by connecting to the network. Setting it up this way is also what makes Pi-hole very powerful for network-wide ad blocking. W…