[CentOS] Caching Nameserver -- Windows client DNS/resolver default issue?

Bryan J. Smith b.j.smith at ieee.org
Wed Aug 10 16:50:52 UTC 2005


William Warren <hescominsoon at emmanuelcomputerconsulting.com>
wrote:
> Let me restate what i am trying to do and the original
> error:  I have a centos-4 machine that acts as a samba
> file server and my ntp time server.  I now want to have it
> be a dns caching name server for my network since my 
> firewall's caching is not long enough for me.

Are you sure it's the server?

Most firewalls these days are BSD (including variants
like VxWorks) and Linux network stacks and use BIND or
another POSIX DNS service.

As I mentioned in a previous post:  
http://lists.centos.org/pipermail/centos/2005-August/009553.html
 

Windows NT5+ (2000+) client systems have a _flawed_,
_default_ logic to "hold down" DNS resolution upon failure. 
That means if a DNS resolution fails, Windows clients will
_not_ requery the server _until_ that timeout passes.  There
is a registry hack to change this as follows:  
[ From http://www.winguides.com/registry/display.php/1203/ ]

  'To change the DNS cache timeout for negative responses
   (where a lookup failed).
   Windows 2000 - Create or modify the DWORD value called
   "NegativeCacheTime".
   Windows XP and .NET Server 2003 - Create or modify the
   DWORD value called "MaxNegativeCacheTtl".
   Set the value to equal the required timeout in seconds
   the default is 300 (5 minutes).
   Restart Windows for the changes to take effect.'

It's my #1 recommendation until you resolve the problem.
UNIX clients/resolvers _never_ (AFAIK) cache a "failure,"
only Windows -- which I think is flawed, but there is a
reason for it (that has to do with legacy SMB file/print).

Regardless of what solution you come to on the server,
consider doing the above.

-- 
Bryan J. Smith                | Sent from Yahoo Mail
mailto:b.j.smith at ieee.org     |  (please excuse any
http://thebs413.blogspot.com/ |   missing headers)



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