General Question regarding DNS Setting in WAN and LAN

dffvb

Occasional Visitor
Hi there, when changing the DNS settings of my Asus RT AC88U pointing to my PiHole I stumpled uppon two different setting. 1. WAN DNS which updates really quickly and second LAN DNS in the DHCP settings, which seems to be more of depper change, at least the processing of the changes takes longer.

I am pretty sure, here are people who knwo the differences and the implications :)
 

dave14305

Part of the Furniture
WAN DNS changes only require dnsmasq to restart to take effect. LAN DHCP DNS server changes will restart the network stack so DHCP clients will renew their leases and get the updated DNS settings via DHCP. Takes much longer for everything to initialize. And it’s disruptive, so timing is important with everyone at home.
 

dffvb

Occasional Visitor
Thanks a lot. But both do the same right? Leaving both empty leaves me with the DNS from the ISP (or in my case modem / router combo before the 88U) In case they deviate from each other LAN supersedes WAN? And in general when trying different DNS seervices (pihole, adguard) I better change it in the WAN?
 

ColinTaylor

Part of the Furniture
No, they do different things. The WAN DNS is what the router uses as its upstream DNS server(s). The LAN DNS is the server addresses that are given out to DHCP clients which the client uses as it's DNS server(s).
 

ColinTaylor

Part of the Furniture
Ok got it, last question, if I leave it empty, it fetches from the Modem /Router?
If by "it" you're referring to the LAN DNS server field then yes, the router will send only it's own IP address to the DHCP client.
 

MarkyPancake

Senior Member
You can also force individual devices to use a specific DNS server (preset or custom) via LAN > DNSFilter.
 

dave14305

Part of the Furniture
You can also force individual devices to use a specific DNS server (preset or custom) via LAN > DNSFilter.
True on Merlin, but not on stock. But on stock you can assign a unique DNS server per device on the LAN DHCP Server page. But it's not forced like with Merlin's DNSFilter.
 

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