DNS servers randomly alternating between NextDNS and my ISP's (Debian)

[paps]

Hi, thanks a lot for this great project.

I have a very simple setup on Debian Sid, nothing much installed, not even NetworkManager.

I've installed nextdns by doing the recommended sh -c "$(curl -sL https://nextdns.io/install)"

And here's what I get when I look at my dashboard, an alternating resolver (I'm not even refreshing the page):

"Orange" is my ISP. I'm behind their provider router (ethernet) which obviously advertises their own DNS servers through DHCP (if that matters)

When I run sudo systemctl restart nextdns I see

Aug 26 00:28:11 paris nextdns[430529]: Activating
Aug 26 00:28:11 paris nextdns[430529]: Activate: NetworkManager resolver management: exit status 1

in the systemd logs which does not look too good, but then things start resolving (be it on orange or nextdns)

Any idea about what might cause this? Thanks

Context

• Version 1.7.1
• Platform Debian Sid/unstable

[theeddie]

Just want to point out I have the same issue

[whitedragon551]

Also have the same issue, running this on the UDMP.

[paps]

So like I said in my original post, I didn't even have the NetworkManager running.

Turns out that

• installing network-manager (and network-manager-gnome but I guess this one is not needed)
• and changing managed=false to managed=true in /etc/NetworkManager/NetworkManager.conf
• and enabling and starting the NetworkManager service with:
  • sudo systemctl enable NetworkManager
  • sudo systemctl start NetworkManager

fixed my problem.

Seems like there are strong interactions between NetworkManager and NextDNS, I'm not sure exactly why or how. Anyway, that fixed it for me and I don't see anything wrong in having NetworkManager running on both desktop PCs I run

[paps]

Nevermind, I spoke too fast.

What I said above ☝️ is incorrect, it does not fix the problem

Anybody have a clue?

[rs]

Can you please try to disable auto activate sudo nextdns config set -auto-activate=false; sudo nextdns restart then set manually your DNS to 127.0.0.1 in /etc/resolv.conf to see if it resolves the issue?

[rs]

If it still does not work, you might be using a non supported DHCP client that overrides /etc/resolv.conf. Make sure you disable that.

[paps]

Alright thanks, I finally figured it out. Adding (or rather, uncommenting) the prepend domain-name-servers 127.0.0.1; line in /etc/dhcp/dhclient.conf solves the problem

This makes me believe that NextDNS does not work by default on Debian sid. Dhclient regularly overrides resolv.conf with parameters coming from the network.

you might be using a non supported DHCP client

I mean... I'm using all the defaults from Debian sid, I haven't touched anything. What do you think?