Phantom DHCP servers

I recently came across this issue when working with the DHCP servers on the domain at work. Instead of 41 DHCP servers, one for each remote location, the DHCP administration snap-in was showing we had 93! That’s just a few too many.

In order to clean up the DHCP server list, I first opened Active Directory Sites & Services. You have to click View and then Show services node in order to see the available AD services. Then, I expanded Services and clicked on NetServices to see what DHCP servers (dHCPClass records) were listed. I removed all of the invalid records (but not the DhcpRoot record) and then checked the DHCP admin utility. All of the invalid servers were still listed.

The next step was to use ADSI Edit in order to edit the DhcpRoot record found in the NetServices container. Using ADSI Edit, I browsed to the CN=NetServices,CN=Services,CN=Configuration,DC=Domain,DC=Domain container, substitute your domain name after DC=, right clicked on DhcpRoot and chose Properties. I found another list of invalid DHCP servers when I opened the dhcpServers property of the DhcpRoot record. Once I deleted the invalid servers there, the DHCP admin utility only listed the valid DHCP servers.

It was odd that the list was wrong to begin with. Any time a DHCP server is taken off line it is unauthorized first. Only one or two of the invalid servers were servers that had been replaced due to a server crash that resulted in reloading Windows Server 2003. I may need to set up a DHCP server, authorize on the domain and then decommission it to see if AD is removing them properly. I hope it was just a minor glitch carried over from when the domain controllers were Windows 2000 based.

Patience is something you admire in the driver behind you and scorn in the one ahead. – Mac McCleary

23.Nov.09 Active Directory, DHCP, Networking, Server 2003, Windows Comments (0)