DNS Server value keeps changing!!

Hi,
We have had some problems on our network since yesterday (although nothing has changed). Users have been having problems accessing mail and application servers.
When an IPCONFIG /ALL is done it looks fine and the DNS Servers are listed as 172.16.0.4 and 172.16.0.2 which is correct. When the problem occurs the IPCONFIG /ALL still looks fine but the DNS server IP changes to 192.168.1.1 which is not in our IP range.
I have checke the domain controllers etc., but cant find any reason why this is happening.
Can anyone help before I go insane??
goldsmithwilliamsAsked:
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omarfaridConnect With a Mentor Commented:
Is there a chance that you have a DHCP server on the network with the same IP address?

Try to disconnect the DHCP server for 1 or 2 min and ping the IP address and see if you get reply!

Is this problem is particular to a specific computer or it is with all?

By any means, do you have the scope mis configured on DHCP server?
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omarfaridCommented:
Looks like that you have another DHCP server on the network like adapter connecting you to internet.

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goldsmithwilliamsAuthor Commented:
That could be possible. Is there any way of tracing it?
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omarfaridCommented:
Try to see what is the MAC address of 192.168.1.1.

ping 192.168.1.1

arp -a

This will give you idea of the MAC address which is mostly the adapter MAC address.
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DrDave242Commented:
The next time the problem occurs, do another IPCONFIG /ALL and note what address is shown as the DHCP server.  If it's different from your normal DHCP server, that's your culprit.  Track down that machine and shut off its DHCP service.
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goldsmithwilliamsAuthor Commented:
When the problem occurs the DHCP server is correct but the DNS server is wrong, thats what I can understand. This is an example:

Physical Address: 00-19-DB-32-F9-31
Dhcp Enabled: Yes
Autoconfiguration Enables: Yes
IP Address: 172.16.1.181
Subnet Mask: 255.255.0.0
Default Gateway: 172.16.0.28
DHCP Server: 172.16.0.2
DNS Servers: 192.168.1.1 (should be 172.16.0.2/172.16.0.4)
Primary WINS Server: 172.16.0.4
Secondary WINS Server: 172.16.0.2
Lease Obtained: 8th February 2008 13:29:37
Lease Expires: 12th February 2008 13:29:37

An IP Config /Release then /Flushdns then /Renew puts it right then after a while it goes back to 192.168.1.1
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goldsmithwilliamsAuthor Commented:
This is a problem across the network at the moment.
Can you clarify what you mean by mis configured on the DHCP server?
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goldsmithwilliamsAuthor Commented:
I shut the DHCP server down and pinged it. There is no other device on the network with the same IP as when it shutdown the DHCP ping timed out.
The thing I did notice that was on the DHCP server the DNS IP is 127.0.0.1
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omarfaridCommented:
Is your DHCP server run as DNS server as well?

Do you have multiple scopes set on the same DHCP server?
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goldsmithwilliamsAuthor Commented:
Yes the DNS server is run on the DHCP and I think it has multiple scopes. There is also another DNS server on another domain controller but it doesnt have DHCP.
The strange thing is that the problem only occurred over the last few days and nothing has changed!
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DrDave242Connect With a Mentor Commented:
Open the DHCP console on that server and check the properties of all scopes listed to see if one of them is giving out the 192.168.1.1 address as a DNS server.  If you can verify that it's not listed in the scope options of any of them, check the server options (also in the DHCP console) for the same thing.
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goldsmithwilliamsAuthor Commented:
Thanks for your help. The end result was a port plugged into a VLAN which was on a 192.168.1.x network address.
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