Dns settings changing

Cisco router going into Netgear router. Netgear supplying dhcp to computers and voip phones. Phones plug into wall, computers plug into phones. Computers obtain ip address autonatically, same for dns servers. When computers reboot, in networksettings, the dns server says use the following address, it is the same ip address as the computer. Users have to go in and check the radio button to obtain address automatically. Any idea what could be causing this?

Faulty router? Cisco voip router causing the issue?

Check for a rogue DHCP server first
ipconfig /all

Server running Windows 2012 Essentials. That computers ip address is the one that all workstations pick up and get the ip address changed to in dns servers. When that happens, no one can connect to the server. I am stumped.

So the DNS is being changed to static addresses? Is there any sort of group policy running on that server box?

Again, can you confirm *on a client* that it got it's DHCP settings from the correct server?

a few years ago when I swapped out servers with DHCP roles I had servers picking up settings from 3 DHCP servers before then even though those DHCP servers were turned off. they weren't actually getting addresses from the old DCHP server but filling in settings that the server would have passed out. even though when you did ipconfig / all it was showing the correct DHCP server. drove me mad for several days and I honestly can't remember what it ended up being....:(

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Originally Posted by CeeBee

Check for a rogue DHCP server first
ipconfig /all

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That brings up netgear router 192.168.1.1
Server is 192.168.1.119 which when you bring up network properties on client computers, 192.168.1.119 is inserted into Use the following DNS servers

Quote:

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Originally Posted by CeeBee

Again, can you confirm *on a client* that it got it's DHCP settings from the correct server?

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It should be getting ip address from router not server.

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Originally Posted by 3fingersalute

So the DNS is being changed to static addresses? Is there any sort of group policy running on that server box?

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I have almost 20 of these in the wild, this one is the only one with this problem. No group policy being used. It's a five person office. Using it for backups, off site backups, and remote desktop.

Quote:

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Originally Posted by Mobile PC

It should be getting ip address from router not server.

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Doesn't the router run a DHCP server? ;)

Quote:

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Originally Posted by Mobile PC

this one is the only one with this problem.

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Time for wireshark... see what the server is feeding (the DHCP server).
On another thought, is a phone or tablet getting the correct settings? Or a known clean machine with the firewall on before connecting to network.
Virus or some VPN client comes to mind...

Resolved, finally. AD needs to communicate with client computers. It periodically tries to connect, then it changes the dns to it's own ip address. In network properties, Forwarders tab, added 8.8.8.8. Check box Use root hints. Yay!!!!!