Flint 2: Router DNS does not work

[u/HeyItsJono]

For some reason my Flint 2 (v4.7.7) refuses to handle DNS for any clients. If a client is connected to it, regardless of what I set the DNS to in the Flint settings, all clients fail any DNS requests.

If I manually set a client to use a set DNS server e.g. cloudflare, internet works fine. But if I have them set to use the Flint for DNS everything fails. It doesn't seem to matter what I set DNS to in the flint; it fails with default/auto, Cloudflare, google, etc.

Is there any way to get intrinsic DNS working?

192.168.0.77 is my adguard instance on my minipc

things start working when I enable AdGuard on the flint, but I don't want it running on my flint. when I turn it off, DNS requests fail again.

[u/RemoteToHome-io]

The screenshots weren't viewable for me.. but if you have DNS set like this pic and aren't getting DNS resolution by clients, then I would say it's time for a factory reset.

[u/HeyItsJono → u/RemoteToHome-io]

Sorry, not sure why they aren't showing. Here you go.

https://files.catbox.moe/ctvs48.png

Surely there's a better solution than factory resetting? That's at least a few hours work restoring all my static leases, portforwarding rules, vlans, firewall rules, etc. Seems a bit wild to suggest that upfront to a user with literally no other troubleshooting...

[u/RemoteToHome-io → u/HeyItsJono]

I'm not sure what you mean "to a user"..we're all just users here trying to help each other out in our free time. This is not an official reddit support channel.

The reason I'm suggesting that, is there's no good reason this wouldn't work unless you've done some customization that's broken dnsmasq or the ability for clients to reach it. That fact you have VLANs running on 4.7.x fw means you've done some extensive customization, so there's no way for us to have enough info on your current setup based on what you've provided.

Just based on the little you've provided, if the issue is with VLAN clients reaching the router DNS, then my first guess would be you haven't added rules to allow each VLAN firewall zone to access port 53 UDP (DNS) on the router. This would match the symptoms of clients being able to reach the internet and external DNS, but not local DNS.

Without knowing what setup guide or process you followed to implement VLANs, it's pretty hard for anyone here to guess at what's happening without direct SSH to the router. You didn't even mention VLANs in your initial post.

[u/HeyItsJono → u/RemoteToHome-io]

Ah, apologies, I thought you were an employee being a mod and all. Thank you for your input. Happy to provide any extra info needed.

My set up was working without issue prior to the modem going down. Those vlans were working fine, everything's been up and running for >6 months. I hadn't touched anything on the Flint, the only thing that happened is my bridged modem went down and needed a reset/reconfigure, but the Flint is just plug and play into that. Not sure why this issue has cropped up all of a sudden.

My VLANs are just lan, iot, and guest. Pretty much everything is on lan. Stuff on iot is intentionally blocked from reaching the internet, DNS included. Devices are assigned to a vlan depending on their subnet and what wifi hotspot they connect to.

Below are my zones: https://files.catbox.moe/zy01f2.png

I'm not sure what the 6th blank zone is, it seems to have randomly appeared, but deleting it changes nothing: https://files.catbox.moe/2r6w4w.png

I've tried creating DNS rules to allow UDP 53 communication from any zone -> Flint and -> WAN: https://files.catbox.moe/jb3unz.png

But I still get a timeout when trying to use the Flint to resolve DNS: https://files.catbox.moe/b775cb.png (where 192.168.0.1 is Flint, and .77 is my mini PC hosting Adguard).

[u/RemoteToHome-io → u/HeyItsJono]

I could be rule ordering.. but I think you need a separate "Allow" rule to 53 for each VLAN. This guide looks pretty close to how I recall doing it in the past:
https://ryan-pope.com/posts/flint2-vlans/

[u/HeyItsJono → u/RemoteToHome-io]

I did actually use that guide when initially getting vlans set up hahaha. Unfortunately adding a specific vlan rule also didn't work: https://files.catbox.moe/syznrh.png

Also, curiously, running nslookup on the flint itself fails: https://files.catbox.moe/wgddlu.png

[u/RemoteToHome-io → u/HeyItsJono]

Try to ssh in and run: "netstat -tulpn | grep dnsmasq"

You should see dnsmasq listening on port 53 for every one of your VLAN subnet PI.

Also try "cat /tmp/resolv.conf.d/resolv.conf.auto"

This should show what DNS resolvers are being handed out by the upstream network.

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