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How does Mac OS X deal with DNS server queries?
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Clinically Insane
Join Date: Dec 2000
Location: Caught in a web of deceit.
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I used to think that the manually specified DNS server addresses were queried in the order specified in the network configuration.
For example, my three DNS servers are:
Google: 8.8.4.4
295.ca: 208.72.120.204
OpenDNS: 208.67.222.222
I used to assume that all DNS queries would go to Google first, and then if that fails, to 295.ca, etc.
However, this page suggests they're all used equally.
Why? Also, how long does it wait before it consider a query to have failed?
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Clinically Insane
Join Date: Mar 2001
Location: yes
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DNS lookups in OS X are completely messed up.
It used to be that /etc/hosts was respected first (as it should be), this changed at some point but only for certain apps. This could be fixed in 10.7.3, it seems at least improved, but I'm not certain of this.
I think the server order is round robin. The overall timeout value depends on several factors. If you are trying to get a certain result I'd rely on your /etc/hosts file for that, assuming this is indeed fixed in 10.7.3.
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Moderator  Join Date: Jan 2001
Location: Polwaristan
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The article seems correct for 10.6. I recall doing some packet capture to see what dns was doing. It generally respected my manually input choices but would use other ones (e.g., dhcp-supplied) during high volume lookups.
I just tested 10.7 and it does the same thing. You can see the transition from google dns (first manually input dns) to opendns (second).
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