There are two scenarios I can imagine in where you want to configure the DNS set by PiHole

1. You have multiple PiHole’s in your LAN
2. You have a multi-layer DNS setup

In either case, we can utilize dnsmasq configurations in order to set the DNS option. You should already notice 01-pihole.conf and 02-pihole-dhcp.conf in /etc/dnsmasq.d, we’ll need to create one that is numbered 03-* or greater. I’ll use /etc/dnsmasq.d/03-dhcp-dns.conf as my example.

To set the initial DNS server to be from the router.

dhcp-option=6,192.168.0.1

To set multiple DNS servers

dhcp-option=6,192.168.0.2,192.168.0.3