Setting DNS in Router kills the internet

[deHakkelaar]

Try defaulting your router settings and only enter the Pi-hole IP for DNS on the DHCP service settings page on the router.
Methods 1 or 2 in below FAQ:

How do I configure my devices to use Pi-hole as their DNS server?

Three methods Generally, there are three different methods that will enable devices on your network to be protected by Pi-hole. 1. Define Pi-hole's IP address as the only DNS entry in the router Rationale Only is italicized here for a reason: Pi-hole needs to be the only DNS server because it intercepts queries and decides whether or not they should be blocked. If you have other DNS servers configured, you may be sent to the correct domain, bypassing Pi-hole completely. Because of this, we re…