I think the most general and "best" method on DD-WRT is to:
Services>services>Additional DNSMasq Options:
dhcp-option=6,192.168.1.250
No other changes on DD-WRT are needed. Substitute the IP of your pi-hole for the 192.168.1.250 above. Why do it this way? 3 reasons:
- Per-host tracking on Pi-hole (i.e. logging of DNS requests tied to individual machines by their respective hostnames).
- The ability to resolve hostnames on the LAN.
- Ad blocking/network monitoring provided by Pi-hole.