Just wanted to point out the excellent solution provided by this post. Just disabling my router's DHCP caused "No internet connection" on the router (and for the whole house). To fix it, in short:
- set the router's DHCP to a range of exactly one IP address:
192.168.1.2 -- 102.168.1.2(or whatever your pi-hole address is). - make the pi-hole DHCP's range above that one address.
Additional trick: to prevent clients from appearing as '_gateway' on the pi-hole, change the router DNS to e.g. 192.168.200.200 (or some other non-existent address on your local network). That way, the pi-hole's DNS is the only working DNS on your network, and all clients now reach to it directly (and thus, are identified correctly by pi-hole with their Mac and IP addresses).