ASUS router DNS check fix

Introduction

After updating the firmware of my Asus RT-AX92U to version 3.0.0.4.388_22525-gd35b8fe, I've noticed two DNS requests to dns.msftncsi.com every minute. My RT-AX92U is used as an access point, so there is zero reason to check for WAN availability. Additionally DNS is unchecked in Administration > System > Network Monitoring.

Ok, let's verify the settings in nvram:

dns_probe=0
dns_probe_content=*
dns_probe_host=

Yep, it's not active and there is no host set either. So why is it doing a DNS check? Apparently dns.msftncsi.com was hard-coded as default and the dns_probe setting is ignored.

Solution

ssh into the RT-AX92U and run the following commands:

nvram set dns_probe_host=127.0.0.1
nvram commit

Done.

P.S.: It might also be possible to do this via the UI, but I haven't tried that. Check DNS in Administration > System > Network Monitoring, enter 127.0.0.1 in the field Resolve Hostname, and click Apply. After that one can uncheck DNS and click Apply again, although the disabled state is ignored anyway.