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I search for this a lot and the answer is the same everywhere:

Authoritative servers give either the answer or "NO", the host does not exist.
Non-Authoritative servers use either cache or a forwarder.

please just answer these questions and i'm on my track:

  1. Is a DNS Server that answers an iterative query with "I don't know the answer of that query but here is the address of the DNS who knows the answer" is an Authoritative Server for that query ?
  2. If the answer to the question above is "NO", then does it mean that the Authoritative DNS server is the one that has control over the Zone of the host record ?
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  1. No, it is not authoritative for the name which you asked for in the query. It is authoritative for one of the parent zones, though.
  2. Yes, it's authoritative for all names inside the zone that has been delegated to it (whether there are any records or not).
  3. Yes, if it's authoritative for example.com it's also authoritative for subdomain.example.com unless the latter has been delegated elsewhere.


It's important to note that your questions do not directly address the quoted definitions.

Your quoted definitions describe (a bit oversimplified) how the two types of nameservers operate overall, but your questions are about what type of answer a nameserver will be able to give for a particular query.

As I noted in my answer for question 1, that is a case where you are talking about a nameserver which operates as an authoritative server but which is not able to answer this specific query authoritatively (only returning authority information). This does not mean that this server is also your second category of server (one which honors recursion requests), it's merely that there is a bit of a mismatch between the questions and the definitions and that the definitions are a bit simplified.

To further complicate things, it is also possible to run a nameserver that operates as a mix of both types, but that doesn't seem immediately relevant to any of your questions.

  • (3. is in reference to a third question which was posted a comment at the time. I'm leaving that answer in there for now) – Håkan Lindqvist Apr 26 '15 at 8:06
  • Thank you Håkan Lindqvist. Is this mean that if a DNS Server has control over managing specific namespace records (read, write, modify) , then it is called authoritative and others which can refer to this Server non-authoritative ?! – Shnd Apr 27 '15 at 4:18

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