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In this one network I have, I am moving from a linux infrastructure to a Windows infrastructure. This has been a staged process.

Originally there was no Windows infrastructure. DNS, NIS, and DHCP all came from a pair of Linux servers.

When the Windows servers arrived, we configured an AD zone.

We then moved the DHCP server from Linux to the AD servers. At this point, the DHCP scope was set so that the DNS names and servers were still those on the Linux server.

Once the zone was complete, we changed the DHCP scope to use the AD names and servers instead.

Finally, we tried to decommission the linux servers.

However, some Windows clients are reverting to using the old DNS servers.

You can do an ipconfig /all and look at the network interface -- it will show you the AD server as the DHCP server, and the two Linux nodes as the DNS servers.

The thing is that they do this randomly -- some of them stick to the new servers, and some of them seem to flip back and forth between the new servers and the old servers.

Obviously I can't decommission the linux servers as it will strand several workstations.

I've dumped the scope and searched it for the IP addresses of the old DNS servers -- they are not there. I have tried deleting and recreating the DHCP scope, deleting and re-installing the DHCP service, and deleting everything and cleaning out the DHCP registry mess before reinstalling and recreating everything.

Clients are still reverting.

The scope in question has all-reservations in it, there is no dynamic pool. So recreating the scope isn't terribly painful (I have the netsh commands to recreate the scope and reservations tucked away).

Does anyone have any idea what I'm missing here.

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    Check to see if the Windows domain has a GPO that is overwriting the DNS settings on the Windows machines. – Rob Ramos Jul 3 '15 at 15:46
  • There does not appear to be such a GPO. – David Mackintosh Jul 3 '15 at 18:33
  • After they "revert" are the DNS entries static and/or is the "DHCP server" IP what is expected? If they are static then something: a logon/startup/scheduled task script or GPO are changing it. If the DHCP server IP is not as expected then there is a 3rd DHCP server on the network. – Ed Fries Jul 3 '15 at 19:42
  • Also, IPConfig /all does not show whether DNS is set via DHCP or static, check the GUI Netsh Name="%InterfaceName%" DNS Set Source=DHCP will force to DHCP and can be run via GPO. If laptops are involved then it needs to be changed on both/all interfaces. – Ed Fries Jul 3 '15 at 19:58
  • @EdFries The dhcp server is what is expected after reversion. The GUI control panel says DNS servers are still controlled by DHCP, not statically set. I'll check into the GPO. – David Mackintosh Jul 7 '15 at 10:37
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A few different options:

Option 1

In your DNS settings, expand the tree under the server name. Then, expand the tree under 'Forward Lookup Zones'. Right click on your domain and go to Properties.

Go to the 'Name Servers' tab - is the server listed there? If not, make sure you add it.

Option 2

Open the DHCP Server MMC. Expand the tree under 'IPv4'. Right-click on Server Options, and choose 'Configure Options'. Scroll down to the '006 DNS Servers' option, and manually assign the DNS Servers for clients on your network.

After trying both of these steps, do a release/renew on the clients or wait for their leases to expire and renew. Provided they are all running Windows this should assign the settings to all clients as a default.

  • #1: yes, the servers are listed. #2: yes, the servers are listed. – David Mackintosh Dec 14 '15 at 17:19
  • I don't want to be repetitive - just confirming based on a few thoughts. 1) Are all clients set up the same way? Are they all accepting the GPOs on launch? I've had some before that simply failed to accept the GPOs so things like mapped drives didn't get pushed out. 2) Are there multiple profiles in use on these machines? Or is it mainly one machine per user? Thinking the different profiles may be bringing with them different settings. – txr Dec 15 '15 at 21:01
  • You have probably already tried this, but if not I would also suggest checking the Event Viewer if you can narrow down the time (within 12 hours or so) of when clients revert to the old servers. This may shed light on an instruction causing them to do so. I've solved a few mysteries that way. – txr Dec 15 '15 at 21:12

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