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I have a Windows 7 machine that seems to always have some DNS servers that were retrieved from some previous connection. They seem to take precedence over the DNS servers that my current connection handed out over DHCP. I think they came from my school ( The two rogue servers are ipv6 ones.

Here is the output if ipconfig /all

DNS Servers . . . . . . . . . . . : 2607:ea00:102:2001::53
NetBIOS over Tcpip. . . . . . . . : Enabled
Connection-specific DNS Suffix Search List :

Anyone have any thoughts on how to purge these out, or how they came about? They only show up on my wireless connection.

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Have you tried ipconfig /flushdns? – Alex Apr 10 '13 at 16:05
@Alex yes, they still linger – Andy Apr 10 '13 at 16:17
Are the DNS servers static in the network settings under IPV6? – xpda Apr 10 '13 at 18:29
@xpda No, everything under the ipv6 setttings is automatic – Andy Apr 10 '13 at 19:42

This also happened to me after connecting to a network with a "rogue" DHCP server on it (there were 2 DHCP servers, one linux machine running dnsmasq and a Windows Server 2008 box running MS-DHCP on the same network segment). Each server was giving out different settings and somehow this corrupted something with my WiFi adapter's settings PERMANENTLY. It was one of the strangest and most frustrating problems to troubleshoot. I tried everything - manually setting DNS settings, disabling IPv6, flushing DNS, deleting wireless network settings, switching user accounts, updating drivers, disabling various protocols, and disabling/enabling the adapters. Nothing worked!

The way I eventually "fixed" it was:

  1. launch a command prompt
  2. enable showing hidden devices by typing: set devmgr_show_nonpresent_devices=1
  3. launch Device Manager
  4. click View > Show Hidden Devices
  5. manually Uninstall whichever Network Adapter (Intel Centrino Wireless-N 1000 in my case) as well as any other hidden adapters that you are not using, and then reboot the machine.

After this, the network adapter(s) should be re-discovered and installed automatically. Since doing this, the rogue Search Domains and extra IPv6 DNS server has not returned, and it's been about a week now. Good luck!

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