Why are devices trying to hit an outside DNS server?

[blueyetisoftware-jason]

I have configured 3 sonoff fan controllers. They are working fine, but I recently tried to restrict their network access to local only, blocking internet access. They continued to function, but my router was logging errors that they couldn't contact an outside DNS server. I don't have logs of which server that is. I only see a DNS failure going to the outside world.

What is it trying to hit? Why? Can I shut it off?

[RavenSystem]

HAA uses DNS server given by the DHCP server. By default, only fallback NTP server uses a DNS name https://github.com/RavenSystem/esp-homekit-devices/wiki/general-configuration#ntp-server

On update process, there are GitHub servers involved by default.

[blueyetisoftware-jason]

Thanks. So I would need to configure it to either drop NTP entirely or have it use a local server. Is that the only outside DNS that would be performed? I understand firmware updates if I trigger those. I was thinking that it would not hit those if I didn't trigger an update. Does it automatically check for updates?

Is there a list of domains we can allow instead of having open internet?

Thanks again.

[blueyetisoftware-jason]

I ended up whitelisting pool.ntp.org for UDP Port 123 (NTP), but now see a different error related to DNS: "DNS response not seen". Again, device is functional, but the router is seeing it error out in the logs.