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SBS 2008 DNS Issue

Posted on 2014-11-13
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Last Modified: 2014-11-24
We have a SBS 2008 server which is the main DNS server. Randomly it stops people surfing the internet until the DNS Service is re started. All is fine again after restart but will drop at some point. No errors are flagged in the event viewer.

Any ideas?
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Question by:grovenetsupport
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by:Abdul Khadja Alaoudine
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Enable DNS Debug Logging by going to Properties of the DNS server --> Debug Logging --> Enable logging

Also check System event log for DNS service related issue.
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by:Asif Bacchus
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Are you configured to use DNS forwarders or root hints?  I find root hints can cause this issue, but forwarders seem to work nearly flawlessly.
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by:David Atkin
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I would agree with asifbacchus here.

Change to DNS forwards if you're not already.  Googles DNS has always worked for me:

8.8.8.8
8.8.4.4
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by:grovenetsupport
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Thanks guys but I had already tested the Google Servers albeit only 8.8.8.8 so I have added the other to see if it helps
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by:Asif Bacchus
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Good that you are already using forwarders.  When this DNS issue happens, do your clients still have network connectivity to the server, or is the NIC cutting out entirely?  Can the server itself still resolve DNS queries or does it fail also?
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by:grovenetsupport
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All good bar internet. I can use logmein to get to server but cant surf net till dns server restarted
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Asif Bacchus earned 500 total points
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I know you said you are using forwarders, but can you verify you are not *also* using root hints?  With root hints, there is a well known issue with the DNS cache not flushing properly.  This could be the case here also.  Before getting to that, let's rule out a few other things.

Does you DNS server actually stop, or do you just have to restart it?  Also, since you tagged this with SBS, I'm assuming this is the only DNS server, correct?  If so, do you have the localhost (127.0.0.1) listed as one of your DNS servers in your forwarding setup?  It definitely should NOT be on that list.

If that's all working, you can try the cache refresh fix as follows (MS Fast-Publish Article 968372):

Edit the registry as follows:

HKLM\System\CurrentControlSet\Services\DNS\Parameters
Create a new 32-bit DWORD value called MaxCacheTTL with value 0x2A300 (172800 in decimal)
Quit regedit and restart DNS service

Let's see if this helps.
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by:grovenetsupport
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It is set to use Root Hints if no forwarders or is that not what you mean?
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by:Asif Bacchus
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Yes and no :-P  That is a good setting and it is the recommended setting.  It could be that your calls to the Google DNS servers are failing (network load, etc.) and then your server is resorting to root hints.  In that case, then the cache issue comes into play and that's why I suggested the registry change.

I tend to avoid this problem entirely by pointing my forwarder to my BSD gateway/firewall box, which handles DNS (IMHO, please no flaming here!) much better.  However, if you don't have this option (i.e. a solid router with enough memory) then try the registry fix and let's see if that clears up the issue.
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by:grovenetsupport
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Ok I have applied the registry fix and will see what happens
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by:hecgomrec
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Don't know your scenario, but some times a rogue DHCP server can cause surfing problems.

If the problem arise one more time check that all stations have the right IP, Mask, Gateway and DNS assigned to their NIC, check also the server.  If you find a different dns or IP there you should try locate the offending device.
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by:Asif Bacchus
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I'm guessing it was the registry fix that helped you out?  Just so you know, that means that your server is resorting to root hints at least occasionally so you *may* want to take a look at your DNS setup at some point and maybe try using different servers for your forwarders.

In any case, glad you go the issue sorted out!
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by:grovenetsupport
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Thanks for the heads up its not easy walking into someone else's nightmare that's why I love this site
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