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DNS settings in W2K3 - Learner question

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  • DNS settings in W2K3 - Learner question

    Hi guys,

    I have a Q about DNS settings in W2K3 server. Specifically the Minimum (default) TTL field, on the SOA tab, of the zone properties.

    In my MS Press 70-291 book it has a definition of this setting which says:

    Minimum (Default) TTL The value you configure in the Minimum (Default) TTL box determines the default Time to Live (TTL) that is applied to all resource records in the zone. The default value is 1 hour.
    TTL values are not relevant for resource records within their authoritative zones.
    Instead, the TTL refers to the cache life of a resource record in nonauthoritative servers.
    A DNS server that has cached a resource record from a previous query discards the
    record when that record’s TTL has expired.

    Sorry if this is obvious, but does the last sentence above apply to clients as well (because it only mentions DNS servers)? I'm just clarifying this point in order to answer the following question:

    You discover that an administrator has adjusted the default TTL value for your
    company’s primary DNS zone to 5 minutes. Which of the following is the most
    likely effect of this change?
    a. Resource records cached on the primary DNS server expire after 5 minutes.
    b. DNS clients have to query the server more frequently to resolve names for
    which the server is authoritative.
    c. Secondary servers initiate a zone transfer every 5 minutes.
    d. DNS hosts reregister their records more frequently.

  • #2
    Re: DNS settings in W2K3 - Learner question

    It means the record is only stored for 5 minutes on a non authoriative server / DNS resolver and then discarded.

    I would say the answer is B.

    If your DNS server has a record for computerA.domain.internal and your client resolves the IP address to that record, the record will stay in your DNS cache for 5 minutes and then be discarded which means you have to query the DNS server again for that record if needed.

    Hope this helps

    Michael Armstrong
    MCITP: EA, MCTS, MCSE 2003, MCSA 2003: Messaging, CCA, VCP 3.5, 4, 5, VCAP5-DCD, VCAP5-DCA, ITIL, MCP, PGP Certified Technician

    ** Remember to give credit where credit is due and leave reputation points sigpic where appropriate **


    • #3
      Re: DNS settings in W2K3 - Learner question

      Ok i think i've got that into my head.

      Initially i thought the answer was A, but now I realise that this TTL setting is applied only to this servers authoritative records, but will only start counting down when it becomes cached on *another* server (or clients in this case) DNS cache. Hence making the answer in fact B as you said!!

      Thanks for the response
      Last edited by markey164; 18th November 2007, 01:49.