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DNS server not resolving properly

I have a client which recently started having issues with their internet connectivity. I have been trying to figure out what might be the cause but am coming up empty. I think it might be a DNS issue on the the domain controller but may be something else. When I try to Ping a website (yahoo.com) from the controller it has quite a bit a latency and when I go to Whatsmyspeed.com and finally get to the site, need to request twice, it shows the ping as being 24ms and their download speed as 10Mbps which is what is should be but the connectivity is not right which leads me to think there is something wrong with the DNS. I have ran nslookup and it points to the Domain controller yet when I run nslookup google.com <server IP> I get the controller name.domain and the address then a non-authoritative answer that states the DNS request timed out. Timeout was 2 seconds then it returns the site name and address(s).

First how can I see if it is a server issue?
Second how can I see if it is an ISP issue?

Maybe it is the router firewall but don't know where to start. This all started with Sonos not working on the network.

Thanks in advance for your help.
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Tim
Asked:
Tim
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3 Solutions
 
donnkCommented:
Could be couple of things:

1. A user is torrenting capping the connection.

2. Router is faulty.

3. Switch is faulty.

4. Server NIC is faulty.

5. ISP Issue.

It's a case of working through and eliminating them.

Can a pc access the Internet fine ? If it can look at the server if it can't disconnect everyone from the network and test from server, problem gone then hunt down the pc. Problem still then check the server nic has no issues pinging internally if it looks ok swop router/call ISP.

Just try and logically eliminate issues 1 at a time.
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TimSr. System AdminAuthor Commented:
The connection is not Capped. I have content filters enabled on the SonicWall router so that the employees can't do any of that. I am leaning toward the ISP but really don't know how to test that. How can I test the DNS to make sure it is working properly on the server?
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carlmdCommented:
Using nslookup from a pc that does not work (or domain controller), try setting the server to Google.

nslookup
> server 8.8.8.8
Default Server:  google-public-dns-a.google.com
Address:  8.8.8.8
>

Then enter a name and see if it works.

If so, then check the dns resolver settings on the dns server (domain controller?).
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TimSr. System AdminAuthor Commented:
So after digging on this I found that first when I added the AT&T DNS servers to my domain controller NIC it set things in motion with creating confusion on the network. The next thing I found was that when my client moved from Cox high speed internet to AT&T high speed internet the Forward lookup zone, which is where the AT&T DNS server should have went still had the COX DNS servers which have been changed right now were invalid. After fixing all those issues routing and DNS resolution when back to normal. I will give points to all who answered even though non of your answers were correct.
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TimSr. System AdminAuthor Commented:
I found the solution on my own.
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