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DNS Server 2008 R2 Failing

Posted on 2013-12-09
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Last Modified: 2013-12-11
Good Day

DNS server running on Server 2008R2 keeps failing when I do a Monitoring test. When I use NSLookup to resolve a name, it works.

Clients on the network cant resolve names at times.

The DNS server is intermittently not resolving names the last week.
Screenshot of DNS error and NSLookup
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Question by:Yeaktom
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Expert Comment

by:Kyle_Davies
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Have you looked in event viewer to see why it is failing?

You can also type in command prompt ipconfig/register dns and see what is does from there.
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by:ienaxxx
ienaxxx earned 200 total points
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Do you allow anonymous querying of yout DNS?
Because the test should be anon.

Do you listen on the loopback interface (interfaces tab)? because the test could be perfored using 127.0.0.1...

do you allow recursive querying (advanced tab)?

Did you delete something about root hints? Is the server updated (there was an update on servers by microsoft on root hints i can't remember when)? If so can be that the forwarded servers can't resolve the TEST FQDN...

Is DNS configuration stored in Active directory or not?

Hope this Helps.
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Expert Comment

by:vo1ty
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DNS is the Domain Name System. DNS servers convert a domain name (such as example.com) into an IP address (in this case 192.0.32.10). The mapping of names to numbers can change from time to time.

Your computer holds a record of DNS entries to save looking them up every time. This is your DNS cache. You can delete those records (flush the cache) any time you like.

Try flushing the DNS first to get rid of old cache entries

cmd

ipconfig /flushdns


Regards
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Mahesh earned 300 total points
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Check if you have reverse lookup zone for subnet in which DNS server is residing
If not just create one AD integrated reverse lookup zone and also create PTR record for itself

Also ensure that you have Host(A) record for DNs server in domain dns zone (domain.com)

Also ensure that DNS forwarders are working properly by replacing them one by one and telnet them over 53 (DNS port).

On DNS server itself please open Advanced Tcp/IP settings and check DNS Tab.
In DNS tab, check below settings.
ensure that "Append Primary and connection specific dns suffixes" radio button is selected
Ensure that "Append parent suffixes of primary dns suffix" checkbox is selected
Ensure that "register this connection addresses in Dns" checkbox is selected
If there is any deviation in the above settings, its probably you will face name resolution issues

Mahesh
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Author Comment

by:Yeaktom
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Hi

Thanks for all the comments.

@Kyle_Davies : Nothing in the event logs.
@ienaxxx: Yes we do allow Anonymous and Recursion. Nothing was deleted. I think it is stored in the AD.
@Mahesh  I checked everything as you advised.

The dns is intermittent, one minute it works fine next one it is not resolving. When I run NS lookup on www.google.com it resolves the name fine for 30 min, and then suddenly stop for 2 minutes. Then it works fine again for several minutes.
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by:Mahesh
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You can check with your ISP about Public DNS issue
How internal name resolution is working, there is also you are facing same issue ?
Most probably issue exists with ISP end, may be unreliable DNS IPs or its not nearer your location causing packet drops

You may check with below link, how to identify best Public DNS for you
http://www.techsupportalert.com/content/how-find-best-dns-server.htm

Mahesh
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Author Comment

by:Yeaktom
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I think we possibly found the problem.

When we did a ipconfig /all on one of the pc we picked up that the dns for the specific pc was pointing to a Vodafone 3g router. We unplugged the router and so far everything is stable.

Still testing, will revert back tomorrow if this permanently solved the issue.
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Expert Comment

by:vo1ty
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The 2 tests that you are running is not the same,the cmd test on the left hand side of above featured picture is an external Dns test
The test on the Right hand side of above featured picture is an internal test!

Solve the internal Dns problem before testing the external Dns

Regards
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Author Closing Comment

by:Yeaktom
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Thanks for you help guys, at the end it was the 3g router that causes the issues. for some reason the router was set to default settings, could have been lightning or power surge.
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