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DNS Iteration by Windows Xp ?

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  • DNS Iteration by Windows Xp ?

    hi ,
    i had setup a Fictional internal DNS namespace for testing DNS in Windows Network .

    Follow the DNS Structure in attached thumbnail ...


    Are Windows Xp DNS Clients capable of Performing DNS Name Resolution when their Pref DNS Servers reply with Referral answers ? ( i.e Recursion is Disabled on their Pref DNS Servers )

    See the attached Wireshark traces ( captured from DNS Client systems ) ....

    1) First trace is with Recursion Enabled on Preferred DNS Server (in which Pref DNS Server replies with +ve answer to Dns clients Queries)

    2) Second trace is with Recursion Disabled on Preffered DNS Server (in which Pref DNS Server replies with Referral Answers to Dns clients Queries)




    tea time
    Attached Files
    Last edited by harmandeep; 12th February 2009, 20:33. Reason: wrong attachments were posted
    Blog: http://VirtualizationMaximus.com
    OS ... VirTuaLiZaTioN ... MaxiMuS ... Fair, Good, Better, Best



  • #2
    Re: DNS Iteration by Windows Xp ?

    Are you asking us a question?

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    • #3
      Re: DNS Iteration by Windows Xp ?

      seems to me
      Blog: http://VirtualizationMaximus.com
      OS ... VirTuaLiZaTioN ... MaxiMuS ... Fair, Good, Better, Best


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      • #4
        Re: DNS Iteration by Windows Xp ?

        OK, then what is the question you're asking? The "question" in your original post would appear to be rhetorical.

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        • #5
          Re: DNS Iteration by Windows Xp ?

          Originally posted by joeqwerty View Post
          OK, then what is the question you're asking? The "question" in your original post would appear to be rhetorical.
          Are Windows Xp DNS Clients capable of Performing DNS Name Resolution when their Pref DNS Servers reply with Referral answers ?

          is Iteration really possible in Windows Xp Dns clients or is their any fault or mistake in setup ( or whether wht i read in Microsoft press / Sybex 70-291 books was )
          Blog: http://VirtualizationMaximus.com
          OS ... VirTuaLiZaTioN ... MaxiMuS ... Fair, Good, Better, Best


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          • #6
            Re: DNS Iteration by Windows Xp ?

            Originally posted by harmandeep View Post
            Are Windows Xp DNS Clients capable of Performing DNS Name Resolution when their Pref DNS Servers reply with Referral answers ?
            I'm confused too but the answer would be no? If a client gets a dns answer the query is done. In this case the answer from the dns server is 'i dunno' the answer is blank and the query is over.

            If the DNS server is setup as non-recursive, it tells the client 'yo heres my best answer, continue the search yourself' but since your dns servers don't host the right zones this won't go anywhere.

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            • #7
              Re: DNS Iteration by Windows Xp ?

              Originally posted by Garen View Post
              I'm confused too but the answer would be no? If a client gets a dns answer the query is done. In this case the answer from the dns server is 'i dunno' the answer is blank and the query is over.

              If the DNS server is setup as non-recursive, it tells the client 'yo heres my best answer, continue the search yourself' but since your dns servers don't host the right zones this won't go anywhere.

              Sorry , got wrong attachments posted ........
              have a look again .....
              Blog: http://VirtualizationMaximus.com
              OS ... VirTuaLiZaTioN ... MaxiMuS ... Fair, Good, Better, Best


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              • #8
                Re: DNS Iteration by Windows Xp ?

                So what do you want to know?

                With recursion disabled, the server does one lookup and passes that to the client, the client handles the rest of the query.

                With recursion enabled, the server does the first lookup, and all other lookups until it has the answer the client wants, it then gives the client this answer.

                recursion on = load on server
                recusion off = load on client

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                • #9
                  Re: DNS Iteration by Windows Xp ?

                  Originally posted by harmandeep View Post
                  Are Windows Xp DNS Clients capable of Performing DNS Name Resolution when their Pref DNS Servers reply with Referral answers ?
                  There is no clear answer to this because it all depends on whether those records are stored on the DNS zones and its DNS cache.

                  When the client does a DNS query, the DNS server checks first its records on all the zones it host, then the DNS server cache whether recursion is disabled or not.
                  If a record is found the DNS server responds with an authoritive answer to the client. If no exact records are found and recursion is disabled or not supported, then the DNS server returns a negative answer to the client. If however, a similar record is found i.e Cname instead of A record, then the DNS server returns a referral answer to the client.

                  Cheers
                  Caesar's cipher - 3

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                  SFX JNRS FC U6 MNGR

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                  • #10
                    Re: DNS Iteration by Windows Xp ?

                    As per my Understanding this is my answer

                    DNS client first query th e prefered DNS server after this it depends on that DNS server wheather recurssion is enabled or disabled on that DNS server

                    1. Recurssion is Enabled:->>then the DNS server to which the client has forwarded the query will get the answer of that query wheather it is hosting that particular zone/record for that query or not.if it does not hosting that zone/record then it will forward the query to another DNS server or you can say this dns server will perform iterative querries on behalf of client and client will unaware of that and after getting the exact answer of that particualr query it will forward the ans to client and keep the answer in its cache.

                    2. Recurssion is Disabled :-when the recurssion is disbaled then the DNS server to which client has forwarded the querry will look the query into itself(zone/record)
                    and also in cache if it does not have the answer then it will say client to perform iteration on other DNS server then client do the iterative query to get the answer


                    Recursion should be enabled because that will speed up the client machine .
                    IF the recursion is disabled then client need to query each DNS server that will allow more traffic to come to your network.
                    Thanx
                    Vijay
                    ________
                    IPAD CASES
                    Last edited by vsharma; 10th April 2011, 06:33.

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                    • #11
                      Re: DNS Iteration by Windows Xp ?

                      so in the end means , even if the Win Xp Dns Client receives REFFERAL ANSWERS from its Pref DNS Server ... it won,t do Iteration by ITSELF ....... correct me guys
                      Blog: http://VirtualizationMaximus.com
                      OS ... VirTuaLiZaTioN ... MaxiMuS ... Fair, Good, Better, Best


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                      • #12
                        Re: DNS Iteration by Windows Xp ?

                        Originally posted by harmandeep View Post
                        so in the end means , even if the Win Xp Dns Client receives REFFERAL ANSWERS from its Pref DNS Server ... it won,t do Iteration by ITSELF ....... correct me guys
                        The DNS server in its reponse will tell the client that it can't do recursive queries, it will give the client its best answer, the client will then continue the lookup with the "use recursion" option set.

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                        • #13
                          Re: DNS Iteration by Windows Xp ?

                          Originally posted by Garen View Post
                          The DNS server in its reponse will tell the client that it can't do recursive queries, it will give the client its best answer, the client will then continue the lookup with the "use recursion" option set.
                          Exactly sir , the server did infact provided the best answer to the client dns query as depicted in traces , but the CLIENT did,nt do anything with Best answer provided by the Server , no further lookups , and bang , provided a -ve Answer ( did,nt perform queries on its own .... , which i think it was supposed ) ..... which is wht I am Asking ...... why it did,nt perform further lookups on its own on the basis of best answer ........
                          Blog: http://VirtualizationMaximus.com
                          OS ... VirTuaLiZaTioN ... MaxiMuS ... Fair, Good, Better, Best


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                          • #14
                            Re: DNS Iteration by Windows Xp ?

                            It depends what other DNS addresses you have assigned to the client and how those other DNS servers are setup. If you are concerned about DNS lookups failing and you wish to disable recursions on your own DNS servers, you could try adding the last DNS entry as being an ISP's one maybe? The probably issue with the failed lookups will be when a client is looking for an external system and not internal to the network.
                            Last edited by Virtual; 13th February 2009, 19:52.

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                            • #15
                              Re: DNS Iteration by Windows Xp ?

                              Originally posted by Virtual View Post
                              It depends what other DNS addresses you have assigned to the client and how those other DNS servers are setup. If you are concerned about DNS lookups failing and you wish to disable recursions on your own DNS servers, you could try adding the last DNS entry as being an ISP's one maybe? The probably issue with the failed lookups will be when a client is looking for an external system and not internal to the network.
                              This won't do anything, unless the first dns server is offline the second and third are never contacted.

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