WAN DNS vs LAN DNS Bug???

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rohtua

New Around Here
Hi,

I have an ASUS AC86U router which until last night was working perfectly. I use PiHole (running on an Ubuntu Server) for the network. Last night I had an update for the router (to 3.0.0.4.386_42643-g16dc577) once the router was back on I noticed that for some reason that my Ubuntu Server started having DNS issues. After a while troubleshooting I found that the only thing that got the server working again was to change the WAN DNS option to 1.1.1.1. Previously I had this set to the IP of the server as that's where PiHole was. After doing some research into why I had to do this all of a sudden I've found the difference between WAN DNS and LAN DNS. i.e. the WAN DNS is what the router uses to talk to the outside world and the LAN DNS is what the router provides to local devices so they can talk to the outside world.

My question is, after reading about the difference between the two DNS types, how and why was my DNS ever working given that I'd essentially set it in a loop (i.e. the router pointing to the server and the server looking to the router for upstream DNS). What I've read about WAN and LAN DNS makes sense to me but now I'm asking was this a bug with the router that it wasn't even looking at the IP I'd set in the WAN DNS or should it be working in some way and now there is a bug that's preventing it from working?

The router has been left with the WAN DNS pointing to the local server for probably around a year now with no issues and I know it's been working because I've been able to access the internet and run updates etc. Also in PiHole I've been able to see the domain's being blocked and the other traffic statistics it provides.

If anyone can shed any light on this it would be most appreciated.
 

dave14305

Part of the Furniture
See thread:
 

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