dns server

We are having trouble with our DNS.  When I look at DNS on my win 2008 r2 server it shows that the forwarders are not resolving.  I go into them and they say validating but it never happens.  It seems like this issue comes and goes which makes less sense than why it is happening in the first place.  Any info on where I should start to find out a solution?
mkramer777Asked:
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Will SzymkowskiSenior Solution ArchitectCommented:
If it is sporatic then it is working to some degree. I would think that it would be something more server related like a service or other dependancies. WHat have you tired so far to get this working? Have you checked the DNS logs on the server? Have you tried restarting the DNS service? Remove and re-add the Forwarders?

Also try removing "use DNS root hints if forwarders are not available"

Will.
FOXActive Directory/Exchange EngineerCommented:
The first thing I would run on the failing server at a command prompt is dcdiag .
Check for any failures
mkramer777Author Commented:
Re-adding the forwarders did the trick.  Any ideas on why this might be happening?
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mkramer777Author Commented:
This time re adding the forwarders did not work.  Not sure if that is what it is.  Nothing will validate again.  Here is the weird part.  I have noticed that this happens every day around 10AM.  Any ideas with that piece of info?
FOXActive Directory/Exchange EngineerCommented:
I want you to go in to control panel >Administrative Tools> Task Scheduler .....check in there to see if anything out of the ordinary is launching at the time you have mentioned
mkramer777Author Commented:
Figured it out.  Went into the event viewer and saw the word "SHUN"  Our Cisco Firewall was for some reason shunning the DNS servers.  The shunning would happen for 1 hour a day and then release because the firewall settings were set to do it that way.  I whitelisted the DNS ip's so they cannot be shunned again.  Very weird.  Anyone have this happen to them before or heard of something like this happening?  Odd that the firewall would think the DNS servers were a threat.

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FOXActive Directory/Exchange EngineerCommented:
Nice find...
Brian BEE Topic Advisor, Independant Technology ProfessionalCommented:
mkramer77, if you feel yours was the only correct answer to this problem, please accept it as the solution so the close process will begin and the question can be made available to help others.

Thanks,
Brian (TBone2K)
Topic Advisor
mkramer777Author Commented:
Did some research on the topic and found out to look into the event viewer.  Saw the shun word in there and went from there to find out it was a firewall issue.
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Windows Server 2008

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