How to remove an old long gone DHCP server from Active directory and DHCP on Windows 2003.

Open ADSI edit.

Configuration-> Services- > NetServices

Checked the properties of: CN=DhcpRoot

Then edited this attribute: dhcpServers

There was one server listed in there:

i172.17.5.1$rcn=cdc.domain.com$0x00000000$dcdc01.domain.com$

This was the one that seemed to be left hanging around.

Took a note of the settings just incase then deleted it and clicked “OK” to apply the settings.

Checked the DHCP MMC snapin under the “Manage Authorised servers” and its gone! harrah.

http://blogs.technet.com/b/networking/archive/2009/02/27/old-dhcp-servers-appear-in-the-list-of-authorized-servers-after-a-domain-rename.aspx