Hi everyone,
the FAQ says that to configure my router's DHCP options to force clients to set their DNS server as your Pi-hole I should only set up one static DNS-server. The problem is that my FritzBox needs always two, I'm not able to set up only one adress. What should I enter as alternative?
Try just setting one and leaving the alternative blank. Most routers let this happen even though there are two fields available.
Also note that we have had many users that have trouble with Fritz!boxes.
Otherwise, try adding the same ip for both servers. 
That's works with other types af router's.
Alternatively, you could enter an address that you know is invalid-- such as 1.1.1.1, or any other unused RFC-1918 address not in use on your network (192.168.x.x, 10.x.x.x, 172.16.x.x).
I would imagine Jacob is right in that your router should allow you to leave the second entry blank. I would also think aqqlejak's suggestion would work on just about any consumer router.
Thank you all for your replies. Everytime I leave a field blank (the second alternative one) I get a error message that says that I've to enter a second DNS for IPv4 and IPv6. What I've done now is to add as a second IPv4 and v6 the ones from OpenDNS (Familytype or what ever they are called).
Greetings.
I believe you are configuring DNS on the wrong page. This is for accessing the Internet and not for your internal network. Please try Heimnetz -> Heimnetzübersicht -> IP-Adressen
This works for me on my 6490 Fritzbox.
