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Win 7 client DNS server settings keep changing.

i have a problem with one laptop running Windows 7 Pro.
The DHCP server (2008 R2) is configured with a scope of 20 addresses and every address is mapped to a specific laptop via reservations.
Within the scope options, 006 DNS is configured for our two internal DNS servers. (We arent on a Domain- only a workgroup).
The 006 DNS scope option used to point to two different external DNS servers.
One laptop out of the 20 keeps reverting back to the ip addresses of the external DNS servers which are no longer online.
If i do a ipconfig /flushdns on the client,  and ipconfig /renew the results shown in ipconfig /all show the correct two internal DNS servers,   after about 3-4 minutes, if i do another ipconfig /all, the PC's DNS servers have changed back to the old incorrect ones.
The laptop has had a new OS installed and the problem persists,
I have also set the 006 DNS options directly against the reserved ip address.
I have searched the registry of the server for the old dns ip address and its not present.
I have flushed the dns cache on the DHCP server.
Any ideas.
1 Solution
Nick RhodeIT DirectorCommented:
Is there an alternate configuration setup on the laptop's NIC under the properties of the NIC?  another place to check is in the advanced TCP/IP settings of the NIC under DNS.  Is there anything in there under append?
Rick_PenneyAuthor Commented:
Hi, many thanks for your reply, both of these entries are blank.
I thought the problem may have been with the laptop which is why i did a clean install on a new hard drive so all settings are default. As its still doing it i guess its something on the server but i cant see what?
Jason WatkinsIT Project LeaderCommented:
Is there another DHCP server on the network which may be handing out those addresses?
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Rick_PenneyAuthor Commented:
no, there is only the one DHCP server, and an ipconfig /all shows the dhcp server as the correct one.
would one of the sysinternals tools show where its picking them up from?
Jason WatkinsIT Project LeaderCommented:
PSList might be able to show you the process that is picking up the IP address, but it might not tell you where it is coming from.
Rick_PenneyAuthor Commented:
I think i might have sorted it, i'll post back in 10 minutes
I'd start by identifying if third party software is causing this to happen.  

The easiest way to do so is to open MSConfig and disable all NON MICROSOFT services.  Check the box to hide Microsoft Services and uncheck the remaining items.  Also review the Startup tab to disable any startup items that are not absolutely critical to system operation (almost all of them should be non critical).

Once the changes are done, reboot the machine and check for issues again.  If you confirm the issue is gone, go back into MS config, enable half of the disabled services and/or startup items and test for the issue again.  Rinse and repeat until you've narrowed it down to a few items to help focus your troubleshooting efforts.
Rick_PenneyAuthor Commented:
Hi, My Mistake, i replaced our DHCP server way back and the old server became the DNS server, i had de-activated the DHCP scope but the service was still running.
I noticed in the Laptops event log that the DNS server was denying DHCP requests.
i have now disabled the DHCP server service on the DNS server and so far it looks ok, really weird how it was only affecting the one laptop when all the others were also present in the deactivated scope on the old server, Grrrr,  thank you to everyone that repied to me, its much appreciated.
Jason WatkinsIT Project LeaderCommented:
Glad to help. Thanks for the points!
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