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Kevin Burke
Asked: 2012-11-08 09:57:44 +0800 CST

Which NS record will dns lookup use?

  • 772

If I have contradictory NS records for my domain:

dig +trace example.com

example.com.        172800  IN  NS  ns1.webfaction.com.
example.com.        172800  IN  NS  ns2.webfaction.com.
example.com.        172800  IN  NS  ns2.mydyndns.org.

Which one[s] will be queried by my DNS client? Does the ordering matter? How can I tell the ordering?

networking

3 Answers

  1. Best Answer

    The ordering in which the lists are presented to you is randomly ordered in most cases. But you (as the dns-admin) can also configure sequential output (round-robin) or static output. Depends on the administrators mood.

    Which entry a client chooses is also up to the developer of the client.

    dig +trace picks a random entry.

    In any case, the only reason for this is load balancing. If all servers are running fine it doesn't matter which entry you actually use.

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  2. I don't see the same output when running the same command.

    But to answer your question, a random one will be chosen and the order you list them in does not matter. You can see this with successive runs:

    $ dig +trace inburke.com

...
inburke.com.        3600    IN  A   108.59.11.111
;; Received 45 bytes from 173.230.141.144#53(ns4.webfaction.com) in 96 ms

$ dig +trace inburke.com
...
inburke.com.        3600    IN  A   108.59.11.111
;; Received 45 bytes from 178.79.142.142#53(ns2.webfaction.com) in 8 ms
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  3. I believe that the resolver uses round robin methodology to query DNS hosts.

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