Hello there,
I’ve recently set up a Synology NAS and set up Homeassistant (Virtual Machine) to replace my Raspi running iobroker.
I then wanted to add PiHole to my NAS, failed (root cause solved I think) and found AdGuard.
So I used the AdGuard Home Integration in Homeassistant.
I pretty much use the basic configuration you can find in several youtube videos.
The only thing I added was an upstream DNS - my FritzBox to enable me to use fritz.box instead of the IP. But that’s it.
Added the correct IP as DNS in my FritzBox and everything was working perfectly fine at first.
After half a day, the network on my PC just suddenly broke down to almost nothing.
I figured it would be the repeater I was using, so I reset that one and reconnected it to the router, and it looked fine. Half an hour later, same issue. Network just suddenly drops to almost no connection.
After a couple resets I found that connecting the repeater to the router was always resulting in a slightly different state. Something was always corrupted during the linking between repeater and router. But it was always something different. Options showing differently, connections not showing up on one device but working fine, Fritz users being synced or not synced, etc.
At one point I got it “looking” fine, and it was working fine for nearly a full day.
But last night my network was completely gone. The actual DSL connection was gone, after I was connected again everything was fine. For a few minutes.
Again, suddenly the connection from my PC dropped down to like 0.01mbit/s.
Long story short: it must be the AdGuard DNS.
Disabling AdGuard protection in the AdGuard Home integration didn’t do anything.
But when removing the AdGuard DNS entry in my FritzBox and renewing my DHCP lease, the connection was perfectly fine.
Adding the DNS entry and renewing the DHCP lease again → instantly pretty much no connection whatsoever.
I know it can’t be the repeater, because I can reproduce the exact same thing when connecting my phone to the router wifi instead of the repeater.
Right now it’s at a point where if I have the AdGuard DNS set in the router config, my phone would connect but show “no internet”.
Removing DNS entry, trying to connect again → everything’s perfectly fine.
So, my issue is:
The AdGuard DNS slows down my network to a point where literally nothing is working.
And I have no clue why.
I didn’t find anything similar unfortunately.
“Connection slow” and stuff like that, yes. But nothing that’s about the connection basically being non-existent.
If anybody would have any idea what I could be doing wrong, that would be highly appreciated!
Especially since it was working fine after initial setup, and then - without changing anything - got a bit bad, then worse, and now at a point where I can’t use it at all 
