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Client connecting to wrong DHCP Server

Posted on 2010-11-08
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Last Modified: 2012-06-27
I have about 5 users who use laptops running windows xp on our network. Some of them (not all) get connected to the wrong DHCP server. When i do an ipconfig/all on these clients, i see the IP address of the DHCP server they are connected to is that of a Windows Server 2008 server that i have running. The problem is that the server is not configured as a DHCP server.

Why would some client be connected to the correct DHCP server and some would not? Any thoughts on how i can fix this?

Thanks
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Question by:jkpc21
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by:OxygenITSolutions
ID: 34087388
DHCP should be allowed/blocked through your network equipment.
Anyone can configure DHCP on a laptop and cause issues on a network.

If you allow only one DHCP server through your network, then you should eliminate this issue.
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by:jkpc21
ID: 34087480
How do i allow only one dhcp server on our network? The DHCP server they are connecting to is one of my server that is not configured as DHCP.

Thanks
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by:sweetfa2
ID: 34087499
if it is ansswering dhcp requests it is configured as such.  check the services for it.  it may also have dhcp-relay configured
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by:davorin
ID: 34087548
Maybe the DHCP server is not on that server, but you have in network another device with the same IP address and DHCP server enabled.
Have you tried to access that IP over web browser on the problematic PCs? Maybe this way you can find out what this device is.
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by:wantabe2
ID: 34088477
That server is configured as a dhcp server. Click start-run type in services.msc and look for the dhcp service and stop it. Then go into configure my server and remove the dhcp role
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by:jkpc21
ID: 34088839
Here is a screenshot of the server roles enabled on the server.

I also double checked all devices on the network and no other device is setup as a DHCP server and no other device is using the same ip address as the server.
Server-Roles.jpg
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by:davorin
ID: 34088874
"and no other device is using the same ip address as the server."
Can I ask you how have you checked this?
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by:jkpc21
ID: 34088902
I went through all internet enabled devices connected to our network.
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by:jkpc21
ID: 34088918
When i type the ip address from the problomatic machine, it takes me to a IIS7 welcome page. Now IIS is installed on the server with that ip address.
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by:jkpc21
ID: 34088923
It actually goes to the IIS7 welcome page when i type the ip from a working machine as well
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by:davorin
ID: 34088956
OK, thanks.
That is a little bit strange as you don't have DHCP server installed on that machine as still it is acting as DHCP server. I have proposed to try that, because some users are connecting equipment to the network and administrators are not informed about that.
Do you have some other "third party" software installed on that server that it is acting as DHCP server.
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by:jkpc21
ID: 34088979
Aside from the antivirus software, there is nothing else installed on the server.
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by:OxygenITSolutions
ID: 34088996
Is the DHCP relay on your router pointing to your server?
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by:davorin
ID: 34089008
Well, there is one test to be sure, but I think you can use it off working hours.
Connect only that server and a DHCP enabled client to a standalone switch and see what IP address it is getting the client. DHCP clients normally gets IP address from DHCP server who answers their request first.
What is IP address of that server? (192.168.0.1 or 192.168.1.1? )
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by:OxygenITSolutions
ID: 34089018
On that subject, what is the IP address you are getting? It may be a self assigned one.
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by:jkpc21
ID: 34089047
I just saw that the default gateway is also incorrect on the client machine. So not only is the dhcp ip address pointing to my server, the default gateway also has the same IP address.

The ip address that the client is getting is correct, its the default gateway and dhcp server thats incorrect.
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by:OxygenITSolutions
ID: 34089066
Check the Gateway address. Type it into a browser and see if it asks you for a password and sometimes that reveals the source. Use http and https . If you recognise the gateway IP address, check that device.
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by:davorin
ID: 34089068
And that is what?
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by:davorin
ID: 34089100
I meant what IP address of DHCP server you get...
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by:jkpc21
ID: 34089125
The gateway address that it is giving me is that same as the dhcp address it is giving me. When i type them into the browser it takes me to an IIS7 welcome page.
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by:davorin
ID: 34089180
Try the suggestion at my comment ID: 34089008
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by:wantabe2
ID: 34089250
do you have RAS setup on a Win server somewhere on your LAN?
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by:jkpc21
ID: 34089301
No RAS server
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by:OxygenITSolutions
ID: 34089468
Can you go start run \\gatewayipaddress\c$ or a known share on the problem workstation and one on a correct workstation and confirm it is in fact the same server and not some other server with the same ip.
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by:jkpc21
ID: 34089500
I think i may have figured it out. On one of the machines that was having the problem i restarted the wireless zero configuration service and once i did that the machine picked up the correct information and was able to go online without any problems. I'll have to wait until tomorrow to test the other machines.
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Accepted Solution

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jkpc21 earned 0 total points
ID: 34096009
Just to give everyone an update. I was able to solve the problem on all clients by restarting the Wireless Zero Configuration service. Once restarted, the client was able to connect to the network and obtain all the correct information (i.e dhcp, gateway, ip address).

Thank you everyone for your help and suggestions.
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Author Closing Comment

by:jkpc21
ID: 34130238
The solution to the problem was to restart the Wireless Zero Configuation services on the client machines.
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