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Windows DNS forwarders

Posted on 2013-05-15
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Last Modified: 2013-05-24
I would like to know the difference between the DNS Standard Forwarders and Root hint forwarders. they sound to me redundant.

The conditional forwarder makes sense to me...for instance , you are telling the client if you want to resolve this specific zone name I will send you (Forward) to this DNS (the one specified in conditional forwarders.

but Standard forwarders, seems the same to me as the Root Hints.....it is saying If you need to resolve a name space that I am not aware of I will send you to this DNS .... I guess Root Hint will take care of that without configuring standard forwarder.Please correct me if I am wrong.

Thanks
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Question by:jskfan
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by:Henk van Achterberg
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You are correct but using root hints you are sure that you will get the results as any other server at the internet will get using root hints.

When using a forwarder you may not know the configuration of that server and you may get other results as when using root hints.

I know ISP's which replace NX DOMAIN with their own search landing page (bleg!)
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by:strivoli
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You are correct.

Sometimes, it is better using a forwarder instead of root hints for performance reasons. Since DNS response times are very important for the overall Internet Browsing Speed, many (admins) find out that setting the ISP's DNS server as forwarder performs much better than root hints.
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DrDave242 earned 300 total points
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Forwarders allow you to specify DNS servers that your server will contact for queries that it can't answer.  Typically you'd use your ISP's DNS servers as forwarders, since they're likely to give you a pretty quick response, but you can use any server you want.

The root hints list is a list of the authoritative servers for the DNS root zone.  Like forwarders, these can be used to answer queries that your DNS server can't answer.

One main difference between the two lies in how the queries are conducted:

Root hints use iterative queries, in which your server sends a query to one of the root servers, which responds with a referral to a top-level domain (like .com or .net) server that can potentially answer that query.  Your server then queries that server, which will then respond with another referral to a server that's authoritative for the domain you specified in the query (experts-exchange.com, for example).  This process continues until your server queries a server that's actually authoritative for the specific FQDN in your query, which will then either provide the record requested or state that it doesn't exist.

When you use forwarders, your server issues a recursive query to the forwarder.  A recursive query basically tells the forwarder, "You do the legwork, and I'll wait here for an answer."  The forwarder then goes through basically the same process as shown above  (with some extra steps added in, like checking its own cache) and sends the final answer back to your server.

In a nutshell, your server does more work if you use root hints, but that amount of work is pretty trivial, and you're not likely to notice a difference in performance either way unless you're performing a very large number of DNS queries.

Using forwarders can obviously cause a problem if you only specify one and it goes down for whatever reason.
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by:strivoli
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Any feedback is welcome. Please help us keep EE clean. Close the question if we did help, delete it if we didn't help. Thank you.
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by:jskfan
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Thank you
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