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Is there a way to prevent DNS lookups?

Posted on 2011-03-14
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Last Modified: 2012-05-11
I have a system that a previous administrator "disabled" internet access on. Now we want it to have internet access, but I can't figure out how they did it. Here are the symptoms:

PC is configured for DHCP and receives an IP address and correct DNS entries.
PC can ping and tracert to any IP address.
PC cannot ping or trace to an external hostname: "could not find host XXXX"
PC can use nslookup to resolve domain names.

I'm thinking there is a registry key or some connection specific setting that was changed to prevent this. I can't figure out what is causing this issue.
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Question by:leviatdr
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Expert Comment

by:vervenetworks
ID: 35132375
The easiest way to prevent internet access is the use of a proxy server in Internet Explorer.  Open IE, find Internet Options, typically under Tools or Privacy depending on the version.  Then to to Connections tab, and LAN Settings.  Uncheck the proxy if checked, and test.
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Author Comment

by:leviatdr
ID: 35132451
I already checked that and there is no proxy set.
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Expert Comment

by:vervenetworks
ID: 35132474
Is the primary DNS server on the PC internal to the network?  It may be using some type of DNS proxy through forwarding, such as OpenDNS.  You could try setting DNS to an external server, and test from there to see if the problem lies with the server.
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Author Comment

by:leviatdr
ID: 35132809
Primary DNS is on the same network. I set the DNS server to both the local dns server and resolver1 at opendns. Same results. I can nslookup but not ping by hostname.
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Expert Comment

by:vervenetworks
ID: 35133170
Does the server exhibit the same behavior as the workstation?
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Author Comment

by:leviatdr
ID: 35133258
No, the server and other local workstations resolve names just fine.

After digging through the event viewer, I'm finding Userenv ID 1054: "cannot obtain the domain controller name for your network, an invalid argument was supplied". I know this is a DNS issue, but I can't figure out why nslookup works but standard resolution doesn't. Does NSLookup bypass the local resolver?
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LVL 3

Accepted Solution

by:
vervenetworks earned 250 total points
ID: 35133289
You may try to reset the TCP/IP stack using WinSockFix http://www.softpedia.com/get/Tweak/Network-Tweak/WinSockFix.shtml

NSLOOKUP does bypass the local DNS cache, and directly queries the primary DNS server.  You can specify an alternate server by using the command "server <servername or IP>"  My bet is a broken stack.  Any antivirus software or local firewall software you could try disabling as well temporarily.
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LVL 26

Assisted Solution

by:akahan
akahan earned 250 total points
ID: 35134969
If you go to

Control Panel / Network Connections , right-click on the NIC you're using, choose Properties, choose Internet Protocol (TCP/IP), click the Properties button, click the Advanced button, and then the DNS tab, do you see anything unusual?

Tried uninstalling and reinstalling the NIC?  Uninstalling and reinstalling the TCP/IP protocol?
Ensuring that the firewall is not blocking UDP packets to port 53?
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Author Comment

by:leviatdr
ID: 35138640
Winsock fix did not resolve the issue. I'm going to try reinstalling the NIC to see if that helps.
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Author Closing Comment

by:leviatdr
ID: 35159608
Issue unresolved. User formatted machine. Thanks for trying.
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