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We are running a Windows 2008 R2 DHCP server. We just added a new DHCP server and removed the old one about three weeks ago.

I have an employee who is reporting IP conflict errors every day now for the past week. I checked the DHCP logs and found zero conflicts. I also turned conflict detection attempts up to 1 to try avoiding issues.

The only thing I found in the logs which was peculiar is the amount of times his interface attempts to renew its IP. Here is an example:

30,12/19/13,17:41:34,DNS Update Request,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
11,12/19/13,17:41:34,Renew,192.168.1.109,Galen-THINK.example.com,8C705257C4D2,,941800471,0,,,
32,12/19/13,17:41:34,DNS Update Successful,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
30,12/19/13,17:41:38,DNS Update Request,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
11,12/19/13,17:41:38,Renew,192.168.1.109,Galen-THINK.example.com,8C705257C4D2,,941800471,0,,,
32,12/19/13,17:41:38,DNS Update Successful,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
30,12/19/13,17:41:42,DNS Update Request,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
11,12/19/13,17:41:42,Renew,192.168.1.109,Galen-THINK.example.com,8C705257C4D2,,941800471,0,,,
32,12/19/13,17:41:42,DNS Update Successful,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
30,12/19/13,17:41:49,DNS Update Request,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
11,12/19/13,17:41:49,Renew,192.168.1.109,Galen-THINK.example.com,8C705257C4D2,,941800471,0,,,
32,12/19/13,17:41:49,DNS Update Successful,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
30,12/19/13,17:42:07,DNS Update Request,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
11,12/19/13,17:42:07,Renew,192.168.1.109,Galen-THINK.example.com,8C705257C4D2,,2755917027,0,,,
32,12/19/13,17:42:07,DNS Update Successful,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
30,12/19/13,17:42:10,DNS Update Request,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
11,12/19/13,17:42:10,Renew,192.168.1.109,Galen-THINK.example.com,8C705257C4D2,,2755917027,0,,,
32,12/19/13,17:42:10,DNS Update Successful,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
30,12/19/13,17:42:17,DNS Update Request,192.168.1.109,Galen-THINK.example.com,,,0,6,,,
11,12/19/13,17:42:17,Renew,192.168.1.109,Galen-THINK.example.com,8C705257C4D2,,2755917027,0,,,
32,12/19/13,17:42:17,DNS Update Successful,192.168.1.109,Galen-THINK.example.com,,,0,6,,,

So could this be the reason he is seeing IP conflict errors? If not, how can I further investigate the cause?

Thanks!

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5
  • This looks like a problem with the DHCP client and not the server... Can you provide some more details about the client?
    – Mathias R. Jessen
    Dec 19, 2013 at 16:03
  • 1
    Did you backup and restore the DHCP database when you moved it?
    – Rex
    Dec 19, 2013 at 16:08
  • No, I wasn't able to restore the settings from the old server because the old DHCP server is Windows 2012 and the one we moved DHCP to is 2008 R2. Restoring the settings wasn't working for me.
    – blizz
    Dec 19, 2013 at 17:02
  • I'm scheduling some time to look at the client PC so I can scan the event viewer and see if I find anything.
    – blizz
    Dec 19, 2013 at 17:03
  • Hey did you find what the issue was?
    – Deesbek
    Dec 23, 2013 at 5:34

1 Answer 1

Reset to default
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The conflict may be due to somebody else on the network having the same IP hardcoded onto a device.

I would do an nmap sweep of the network after assigning a static IP (for testing purposes) to the user having the issues .

If you find that 192.168.1.109 is in use on your network you will need to find the device, this will involve tracing mac address via the arp table to the port on your switch.

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1
  • The client that reports the problem is only half of it. There is likely a less compliant device on the LAN that has the same address - something has to create the clash.
    – Pekka
    Dec 19, 2013 at 18:06

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