Primary and Secondary DNS using 2 Raspberry Pi computers

Help
1

I've set up 2 Raspberry Pi devices with Pi hole. Each works great for doing network-wide blocking. However, when I go into my router and add the first Pi as the primary DNS, and the second Pi and the secondary DNS, I crash my internet connection, and my router gives me warning about potential ISP conflict, and moves the router from 192.168.x.x net over to 10.0.x.x.

Using just one of the 2 Pi-holes works fine. Using both doesn't. I feel like this is a simple mistake, though I haven't had much time to play with it yet. It's quite annoying to have to change my router back the the IP I want it at.

2

This sounds like an issue unique to your router. I run two pairs of Pi-Holes on my routers with no issues. Check all the router settings carefully for any settings that may be related to DNS rebind protection or other similar features.

What router are you using - one supplied by the ISP?

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4

@JoseKreif
FWIW. Like jfb, I run multiple Pi-holes on my local network. I am currently using a Ubiquiti UniFi USG as my main router and have it configured to use both of them for DNS service. Doing so has never, in my case, caused the router to crash.

In addition, I have a third Pi-hole that I use for a testbed for beta versions that is also configured as the tertiary DNS server. Again, no crashing.

5

As far as DNS goes, there is only an option to set my own DNS servers, or get some automatically from the ISP.

Using Netgear n6120

Is there special set up required on each of the Pi Hole computers? (maybe something in /etc/hosts) Or should it just work?

6

No special setup. Each Pi-Hole has a different IP, and you provide both of them to the router, which then provides them to the clients.

7

Alright. I'll keep trying then. Might be a PICNIC problem

8

If your Netgear router allows you to configure DNS servers on both the WAN and LAN side, you want to set the Pi-hole servers on the LAN side. That is allow the Netgear's DHCP service to provide these Pi-hole servers to DHCP clients on your local network.

9

Thanks for the input everyone. I seemed to have found the route of the problem. The wireless radio was still active on one of the Pi computers. Both should be using LAN with a static IP. I turned WiFi off on this device and tried to set a secondary DNS again and it worked. That likely explains why my router was detecting a possible conflict.

Though it could be a coincidence. It's weird that it'd worked fine as a DNS server on its own with the WiFi running in the background, but didn't when 2 DNS servers were being used.

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