How to set properly DNS server on OpenWrt device?

[trendy]

@Barney

Okay, but what is the difference specifing it under the wan interface? In both cases the DNS entry appears in resolv.conf.auto.

If wan interface goes down it won't be used.

@Barney

I see no need for internet access for your AP and therefore no need for a resolv.conf. Or did I miss anything?

Package installation or upgrade. It doesn't hurt.

[dsouza]

@Barney

(...)
Why do you need internet access for your AP? Because of the missing dnsmasq on the AP, the AP's clients must get their DHCP information (gateway, DNS server etc.) from your router.

I see no need for internet access for your AP and therefore no need for a resolv.conf. Or did I miss anything?

Package installation and NTP time synchronization.

[Barney]

@trendy

Package installation or upgrade. It doesn't hurt.

@dsouza

Package installation and NTP time synchronization.

Okay, I got it. Thanks for your examples and have a nice day.

[diederik]

What's the difference between that setting (which I think is what https://openwrt.org/docs/guide-user/base-system/dhcp_configuration#upstream_dns_provider describes) and
Network -> DHCP and DNS -> DNS forwardings (I did it via uci following https://openwrt.org/docs/guide-user/base-system/dhcp_configuration#dns_forwarding)?

[egc]

Setting DNS server in LAN or WAN on Custom DNS will add the DNS servers to:
resolv.conf.auto
This file is queried by DNSMasq for the upstream resolvers to use.

This file can easily be manipulated from outside to add/remove the DNS servers (e.g. when using VPN), DNSMasq will monitor this file and reread on change.

This file is not read if the no-resolv directive is set in DNSMasq.

Now enter the Network -> DHCP and DNS -> DNS forwardings this will add the upstream resolvers in the dnsmasq.conf file as server=x.x.x.x and is always read.

In normal use there probably is not much difference and DNSmasq will query resolv.conf.auto and use the server=x.x.x.x as upstream resolvers.

At least that is my understanding but I am not an experienced OpenWRT users.

[diederik]

Thanks!
The thing that confused me is that I didn't see the DNS servers I specified in resolv.conf.auto, but after a grep -r <IP-address-of-dns-server>, I found it in /tmp/etc/dnsmasq.conf.cfg01411c, which I guess is read in somewhere.

The IP addresses I added are OpenNIC servers and I may/might create a script sometime which pings a whole bunch and then enables/prioritizes the ones online and fastest, so having them in resolv.conf.auto seems the better place.

What I did find in resolv.conf.auto was the address of the advertised by peer, which I explicitly didn't want as that would mean my ISP's DNS servers (when deployed as my main router).

[egc]

@diederik

The IP addresses I added are OpenNIC servers and I may/might create a script sometime which pings a whole bunch and then enables/prioritizes the ones online and fastest, so having them in resolv.conf.auto seems the better place.

Agreed

@diederik

What I did find in resolv.conf.auto was the address of the advertised by peer, which I explicitly didn't want as that would mean my ISP's DNS servers (when deployed as my main router).

That is one reason to add your upstream DNS servers in the WAN as that is the place where you can disable advertised by peer (I also always disable that as I do not want my ISP DNS server)