Using OpenWrt Device as DNS Server in Dumb AP Mode?

Installing and Using OpenWrt
1

Hi everyone,

I’m currently using a Fritzbox 5530 as my main router, running the stock OS from AVM since it doesn’t support OpenWrt. The Fritzbox handles all routing and Wi-Fi for my network.

Additionally, I have a TP-Link Archer C6 v2 with OpenWrt installed, which I’d like to use for a separate IoT Wi-Fi network and as a DNS server to resolve local hostnames. In the future, I might also add ad-blocking functionality.

Right now, I’ve configured the Archer C6 as a dumb AP following the OpenWrt guide. While this works for basic IoT Wi-Fi functionality, I can’t figure out how to set it up as a DNS server in this mode.

Here are my questions:

  1. Is it possible to configure the OpenWrt device as a DNS server while in dumb AP mode? If yes, how can I achieve this?
  2. If it’s not possible in dumb AP mode, what configuration changes would you recommend to enable DNS functionality without disrupting my Fritzbox’s role as the primary router?

I’d appreciate any advice or guidance, especially if someone has a similar setup.

Thanks in advance!

2

As long as your dump ap has an IP address and has dnsmasq configured to act as a DNS server what is the issue?

Edit: to main point of a dump ap is that it only bridges layer 2 segments. It doesn't do routing.
If you assign an address ensure the firewall is configured correctly.

3

I also imagined it should work. I’ve given the OpenWrt device a static IP address, and when I set the DNS server on a client device to point to the OpenWrt device, I can successfully resolve my local hostnames. However, I’m unable to access the internet from the client device in this configuration.

I’m not sure what I’m doing wrong.

Do I need to add something specific under Interfaces -> LAN, such as a custom DNS server in the advanced settings? Or is there some other configuration step I might have missed?

4

I guess the OpenWrt router is announcing itself as a gateway (instead of the Fritzbox); can you check which gateway are the clients receiving?

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The Fritzbox gateway should announce OpenWrt as the DNS server, otherwise you'd have to manually change that on every lan host, which is not practical.
Second is that the dnsmasq on the OpenWrt must have an upstream forwarder for non-local name resolving. Could be the Fritzbox stub resolver or your ISP resolver or some open resovler (GoogleDNS, Cloudflare, etc).

6

Yeah, I plan to eventually set the OpenWrt device as the preferred DNS server on the Fritzbox, but for now, I just wanted to test it with a single client to make sure it works as expected.

Normally, I’d configure the upstream DNS in the WAN section, but since I’m using OpenWrt as a dumb AP, I’m not sure where or how to configure the upstream DNS.

7

Well, that’s exactly what I want — for the OpenWrt router to act as the gateway for DNS. But for some reason, it seems there’s no upstream DNS configured.

8

I managed to fix the issue! :tada:

The solution was to:

  1. Activate the "Use default gateway" option under Interfaces -> LAN (seems like I had deactivated that by accident).
  2. Specify a public DNS server (e.g., GoogleDNS or Cloudflare) under the "Use custom DNS server" field.

After making these changes, everything works as expected. Clients can now resolve local hostnames and access the internet through the OpenWrt device.

Thanks for all the suggestions and help!

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