DNS Question

Posted on 2006-03-23
Last Modified: 2010-04-18
I don't pretend to be an expert in DNS ....

But I've got a dual-NIC server, one side pointing to the outside world, the other inside.  The default gateway points externally, as does the DNS.  If I do an NSLOOKUP on the box, I jump to the outside ( UUNet outside address.  But if I type PING and put an internal DNS name in, it knows to use my internal DNS.

My question is how does it know to go external or internal, especially when my default gateway points outward.  So if I work for, and type ping it resolves the IP on my internal DNS, but if I type ping it resolves outside ... where is that decision made???

Question by:canadiense
    LVL 9

    Expert Comment

    If you have a forwarder setup, it will ask the server listed where the dns entry is. I'm not 100% sure how you have your system setup, so I can say for sure on your's, but that's the general idea. If you right click on the DNS server in the DNS snapin go to properties and in those tabs you will find the forwarder section.

    Also, check this out:
    LVL 33

    Accepted Solution

    dual nic

    int Nic:  

    Ext Nic:

    All Windows 2000 and higher clients that participate in an Active Directory domain, must use the internal Windows DNS infrastructure for DNS resolution.  This is because Active Directory is DNS based.  In order for the client or server to "talk" to AD, it would be preferrable to do this using DNS.  Therefore, the internal Windows DNS is very important....and must be used.

    When you create a domain, the domain name (i.e. company.local) is also created.  When a server or client joins the domain, the default behavior is to add the company.local DNS suffix automatically to the clients TCP/IP properties.  by doing this, the client will automatically append company.local to all requests to DNS.

    so, if you look at your TCP/Ip properties...and click on the DNS tab, you should see company.local as one of the DNS suffixes.

    The DNS suffixes are important as this is the domain the client will query for when looking for records.

    For example,

    if a client is looking for SERVER2....  The client will automatically append the DNS suffix company.local to the query to DNS.  So the query actually becomes  This is done by defualt.  if you add another DNS suffix to the client, (i.e., the query appends both...

    In a normal DNS heirarchy, the root internal DNS server will forward outside DNS lookups to ISP DNS servers.  In this way, if the internal DNS structure can not find a record, Internet DNS servers take over the search.

    So, on the company.local DNS servers, they would forward requests if they can not be resolved internally.  When a search for is done, the internal DNS servers will relieze that this request is not for COMPANY.LOCAL domain...but rather for domain.  Therfore, they forward the request to the internet DNS servers to find record WWW.

    LVL 1

    Author Comment

    Man ... that was fast!

    Thanks ...

    CDCOP - I was looking more for how the local station determined the route.

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