It was definetly DNS
this post was submitted on 12 Jul 2024
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me_irl
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A secondary DNS server set in your DHCP options will do no such thing.
The secondary DNS server is only used if lookups to the primary fail, say like when your pihole crashes or something.
The only way it will work the way you think it's going to, is if you set your DNS resolver to use round robin on a list of DNS servers.
Its literally just a backup DNS server address, and is only used should the primary fail, and returning an nxdomain is not a failure.
Please note, I use secondary to refer to the 2nd IP in your DHCP/DNS options, not to a secondary DNS server, which is something else.
Right, we are on the same page but from experience, setting DNS 1 to the pihole and DNS 2 to for example 8.8.8.8 in your DHCP router will make the pihole useless. There are dozens of similar threads across different forums saying the same thing but if you know how to do it please let me know... Example: https://www.reddit.com/r/pihole/comments/864oli/secondary_dns_setting/
Well, after working as some form of systems engineer for the last 17 years, including quite a few where some of my primary responsibilities were looking for DNS servers, this is literally the first time I have come across this.
Also not quite sure what they're doing because my Debian, 2x Windows, 3x Android and occasionally Apple clients never bypass my primary DNS setting. Neither do the server farms I run at work. So who knows.
Yeah, all I could find was vague statements about the DNS server lookup order being "OS specific" and windows specifically being know for "not respecting DNS order", see https://www.reddit.com/r/networking/comments/kb8hvt/dhcp_dns_server_order/
This is also supported by statements from pihole devs: https://www.reddit.com/r/pihole/comments/x2248t/is_it_worth_creating_a_second_pihole_dns_server/ And: https://discourse.pi-hole.net/t/primary-vs-secondary-dns/1536/4
And then there are the hundreds of similar questions which one could take as "evidence by quantity" or whatever.
In that case I'll be very thankful that mine works as I expect and will try not to change anything.