Windows 2008 R2 DHCP – client renewing too frequently

dhcpwindowswindows-server-2008windows-server-2008-r2

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!

Best Answer

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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