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Duplicate IP addresses

Posted on 2013-05-19
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Last Modified: 2013-06-25
We have a DHCP and DNS server running in windows 2008 R2. The problem is that we are getting a number of the same (duplicate) host records pointing to different IP addresses and some conflicting with other hosts
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Question by:dohacollege
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by:EMJSR
ID: 39180109
Check that other network equipment you have in place is not configured as a DHCP server (like a router). Only one DHCP server per network should be configured. If your Windows server has that role, no other device should.

I would also try and manually delete all leaces from the DHCP Management and restart the service, then have people restart their computers.

Alternatively add the following command to a login script and see what happens:

ipconfig /release && ipconfig /renew
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by:profgeek
ID: 39180745
You can also try this from the command line:

ipconfig /all

Then check to see the address of the DHCP server from which a machine has obtained its IP address.  If you do this on all machines and see more than one address in your network, it will indicate that more than one DHCP server is active.  Eliminate all servers except your Windows server and then reboot the machines that were using other DHCP servers.
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Rob Stone earned 500 total points
ID: 39180839
You should check your Ageing and Scavenging settings on your DNS zone if you are getting multiple host records as well.
http://technet.microsoft.com/en-us/library/cc771362(v=ws.10).aspx

Are the host records old or are the duplicate records being generated at similar times?

Is your DHCP scope over utilised?  What is the lease period in your DHCP scope?

As the others mentioned, you can check for rogue DHCP servers too. This tool can help locate DHCP servers:
http://technet.microsoft.com/en-us/library/cc759117%28WS.10%29.aspx
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Author Comment

by:dohacollege
ID: 39196756
We are facing this problem mainly if we move the computer from one vlan to another vlan. Depends on the vlan DHCP server is assigning different IP address but old ip address is not deleting form the dns
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