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I have found that in all my years of use with Macs, multiple OS versions, multiple hardware configurations, that it never queries anything but the primary DNS server. Why is this? We have spun up many different internal DNS servers and have tried specifying both internal and external DNS servers on the client. It will only resolve hosts in the primary DNS and completely ignores any DNS specified after that.

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    I can't accept the premise. I'm using Mavericks and I changed my network configuration to list two IP addresses; the first is an unused IP address locally and the other is a functional DNS server. I can surf the net, outbound ssh works, etc. Net access is slower because queries to the first server have to time out before the second server is tried.
    – Kyle Jones
    Nov 19, 2014 at 19:06
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    DNS will accept the first positive answer it gets. If the first on the list always has an answer, why would it then look elsewhere?
    – Tetsujin
    Nov 19, 2014 at 19:34
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    If it gets a response from the first DNS lookup it won't try again with another DNS server, even if the first response is NXDOMAIN. All your DNS servers are supposed to return the same results; if you're relying on different DNS servers with different results then your architecture is broken.
    – Mike Scott
    Nov 20, 2014 at 6:40
  • OS X can support multiple resolvers, and use the hostname to select which resolver to use. Check out this question
    – Alan Shutko
    Jan 21, 2015 at 17:27

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If it gets a response from the first DNS lookup it won't try again with another DNS server, even if the first response is NXDOMAIN. All your DNS servers are supposed to return the same results; if you're relying on different DNS servers with different results then your architecture is broken.

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  • I spent a day researching and I think every word you say is right. What I don't understand is how internal company domains are supposed to work? They register their dns as a primary one. So the only reason it works is because the OS is optimized to not query all the dns servers at once? Isn't this whole local domain thing flawed then?
    – Tamas Hegedus
    Nov 27, 2020 at 21:28

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