Pihole is not blocking every LAN Client / not resolving local Clients

[fellpower]

Hey

I normally use pihole on my raspi 3 - but now, i have a server (minisforum HM80) - and i switched my pihole on that server. after that, pihole have some strange behaviors.

My setup:

• Pi-hole [v5.16.2}
• FTL [v5.22]
• Web Interface [v5.19]

Network:

• Fritzbox 5530 Router (192.168.0.1)
• Server (192.168.0.55) - with PROXMOX
• Pihole (192.168.0.240) as a LXC Container on that Proxmox System

In my Fritzbox Internet Router i put in the 192.168.0.240 as a local DNS Server. On the Raspi it works like a charm, but on that server, pihole is strange. The local hostnames ar not resolved anymore, so my clients on pihole have only IPs, no hostnames (that worked on raspi).

Then, some clients, that using the my Wifi (Phones), seem to be using pihole, but the not blocking advertisements. The only thing i can see is google...but no blocks. there using the normal wifi settings, so the Fritzbox Router will give them the local DNS (pihole), as DNS server.

Any ideas, why some WLAN Clients have that issue, and how can i fix that name resolving?

EDIT: Added Diagnostics - https://tricorder.pi-hole.net/oKpIGlHl/

[yubiuser]

@fellpower

The local hostnames ar not resolved anymore, so my clients on pihole have only IPs, no hostnames (that worked on raspi).

Did you enable Conditional Forwarding on your Raspi but forget to enable it in your new Pi-hole instance?

@fellpower

Any ideas, why some WLAN Clients have that issue, and how can i fix that name resolving?

As you have a working IPv6 connection even with global IPv6 addresses I suspect the phones prefer IPv6 over IPv4 and bypass your Pi-hole.

[fellpower]

Im not using a raspi ^^

i have v6 in my local area - so maybe thats a prob - ill check that

[Bucking_Horn]

@yubiuser

Did you enable Conditional Forwarding on your Raspi but forget to enable it in your new Pi-hole instance?

@fellpower

Im not using a raspi ^^

We are aware of that.

yubiuser asked about a particular difference between your previous RPi installation and your current one, namely Conditional Forwarding.

You could check the DNS resolvers a specific machine is aware of, e.g. by running the following command on a Windows client in your network:

ipconfig /all

The relevant output would be the list of IP addresses under the DNS server section.

[fellpower]

okay, i fixed that conditional forwarding problem. never touched it - and i have to switch it on (never switched it off).

and now - a few clients HAVE pihole as DNS, others not. so they not get blocked by pihole. most of them are phones in our wifi network. they get the ip from the router per dhcp - so i thought, they get the pihole ip as dns from it, because i set the pihole ip as local dns for them ^^

[Bucking_Horn]

DHCP is strictly an IPv4 protocol.

You are correct to assume that IPv6 may have an impact on clients:
Your router may be advertising its own IPv6 address as DNS server, allowing your clients to by-pass Pi-hole.

If that would be the case, you'd have to find a way to configure your router to advertise your Pi-hole host machine's IPv6 as DNS server or to stop advertising its own.

You'd have to consult your router's documentation sources on further details for its IPv6 configuration options.

If your router doesn't support configuring IPv6 DNS, you could consider disabling IPv6 altogether.

If your router doesn't support that either, your clients will always be able to bypass Pi-hole via IPv6.