DNS query basics

Discussion in 'DNS Server' started by Valdas Adomaitis, Nov 26, 2009.

  1. Hello
    I'm reading on name resolution and experimenting along the way.
    My configuration in question is :
    1. XP computer DHCP
    2. Windows Vista computer DHCP, netBIOS disabled
    Both computers get their address from simple hardware router via DHCP.

    So as i read name resolution in order on Vista machine goes like this:
    a) DNS;
    b) LLMNR (not in our case, because xp without IPv6)
    c) netBIOS (off on vista, because of experiment)

    I suppose in my scenario DNS should be used to resolve names. There is no
    primary DNS suffix on ipconfig /all output.
    if i ping XP by name (without trailing dot) - it does not respond;
    if i use nslookup - it returns the ip address
    if i ping xp by name with a trailing dot - it responds.

    What kind of DNS query does a resolver do if a machine does not have a
    primary DNS suffix and query is made NOT by FQDN, but just a simple name.
    Did my query go to the root dns servers and then got lost in the first ping
    (without trailing dot)?

    Valdas Adomaitis, Nov 26, 2009
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  2. IIRC, if you don't provide a FQDN and the client doesn't have a domain name
    then your client wouldn't ship it off to a dns server, since the dns server
    wouldn't know what to do with it.

    If your client knew of a netbios name server (WINS server) it would send
    this query to this server and if that wasn't available or couldn't find it,
    it would broadcast the query on the local sub-net. After that it just quits
    and comes back with a name not found.

    Paul Bergson
    MVP - Directory Services
    MCTS, MCT, MCSE, MCSA, Security+, BS CSci
    2008, 2003, 2000 (Early Achiever), NT4
    Microsoft's Thrive IT Pro of the Month - June 2009


    Please no e-mails, any questions should be posted in the NewsGroup This
    posting is provided "AS IS" with no warranties, and confers no rights.
    Paul Bergson [MVP-DS], Nov 27, 2009
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  3. In addition to Paul's response, even if NetBIOS is disabled, in an AD
    infrastructure (where the machine is joined with the AD domain name as the
    Primary and Search suffix), it will use DirectSMB to resolve it.

    If not, such as in your scenario, Paul pretty much covered it. Without the
    trailing dot, it is using NetBIOS, but since NetBIOS is disabled, it will
    not resolve it, even if in an LMHosts file.

    The trailing dot forces the client side resolver to treat it as a hostname
    query. However you stated nslookup was able to resolve the host with a
    trailing period. What DNS server was it using? Remember, nslookup is a
    nameserver lookup tool. If it is set to the ISP's DNS (you didn't state
    specifics such as an ipconfig /all of both machines, but I assuming such
    since you have a 'simple' network and also assuming no AD is in the
    picture), then I can't see how it resolved it, whether hostname, DirectSMB
    or lmhosts.

    Please read the following regarding nslookup and the client side resolver

    Microsoft Technet: Nslookup

    Read the following for more info.


    [DOC] Using NSlookupFile Format: Microsoft Word - View as HTML
    If you fail to fully qualify a name query (that is, use trailing dot), ...
    to be a host name and an attempt is made to resolve it using the default
    server. ...
    http://mcse.villanova.edu/Courses/688/documents/Using NSlookup.doc


    This posting is provided "AS-IS" with no warranties or guarantees and
    confers no rights.

    Please reply back to the newsgroup or forum for collaboration benefit among
    responding engineers, and to help others benefit from your resolution.

    Ace Fekay, MCT, MCITP EA, MCTS Windows 2008 & Exchange 2007, MCSE & MCSA
    2003/2000, MCSA Messaging 2003
    Microsoft Certified Trainer

    For urgent issues, please contact Microsoft PSS directly. Please check
    http://support.microsoft.com for regional support phone numbers.
    Ace Fekay [MCT], Nov 29, 2009
  4. Thank you guys, this pretty much covers all my blind spots.

    Valdas Adomaitis, Nov 29, 2009
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