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We have 2 synchronized DNS servers in our domain, both running Server 2003. Upon arrival this morning, I noticed that accessing external websites is very slow however, accessing shares/servers on the LAN is fine. After changing the DNS server on my laptop to an external server ( the speed in which I could access external sites picked up tremendously. What could have changed overnight that is slowing down DNS?

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Try querying the servers using nslookup.exe – symcbean Dec 13 '11 at 14:21
How are we able to tell what changed in your environment over night? You need to look at log files, compare configuration files, take network traces with something like wireshark or netmon, etc. Once you have all of that data, if you still don't understand what's happening, you should come back and open a new question that is far more detailed. – MDMarra Dec 13 '11 at 15:10
I did not expect you to be able to tell me the exact cause of my problem, I was simply looking for some good places to start. I apologize if my question was not specific enough however, it did provide enough information as Mr. Smith pointed me in the right direction with his response below! – user1017477 Dec 13 '11 at 15:43
up vote 2 down vote accepted

You want to see what the forwarding servers are set to on the DNS servers. These are the servers that are used when a record doesn't exist locally (say, when visiting another site on the Internet). One of the forwarders may be responding slowly.

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Forwarders don't have to be set. It's entirely possible that his servers are using root hints, which is the default configuration. – MDMarra Dec 13 '11 at 15:11
True, good point. – Kyle Smith Dec 13 '11 at 15:13
Changed the forwarders and all is well. Thanks for your help Kyle! – user1017477 Dec 13 '11 at 15:44
Except that root hints will be slow and its considered rude/bad practice to use the root as your DNS. Use your ISP's caching DNS. – DrZaiusApeLord Dec 13 '11 at 16:35
@DrZaiusApeLord can you please provide source of your information ? – Sandman4 Dec 13 '11 at 17:08

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