Unable to Unauthorize Windows 2016 DHCP Server

Question

I have a Windows 2016 physical server which I am trying to decommission. I ran into an issue trying to unauthorize DHCP. It kept saying "Null" value in the GUI. I tried using PowerShell and it removed the server but the GUI still showed it authorized. Now one thing I did notice is the IP listed for the DHCP server is a 169.x address which is probably for one of the disconnect nic's. Could this be causing an issue? All of the command line suggestions I have tried have not helped.

Any thoughts...

Answer 1

Ensure that you are performing this task as a member of the Enterprise Admins group.

If so, and the GUI/PowerShell don't work for you, use AD tools instead:

Using ADSI Edit

1. Open ADSI Edit:

• Open ADSI Edit by running adsiedit.msc from the Run dialog or Command Prompt.

2. Connect to the Configuration Naming Context:
   • In ADSI Edit, right-click ADSI Edit in the left pane, and select Connect to.
   • In the Connection Settings dialog, select Configuration as the naming context and click OK.
3. Navigate to the DHCP Authorization Container:
   • Expand CN=Configuration, then CN=Services, and CN=NetServices.
   • The NetServices container holds authorized DHCP server entries.
4. Locate and Delete the DHCP Server Entry:
   • Under CN=NetServices, you’ll see entries for authorized DHCP servers, typically named CN=<IP Address of the DHCP Server>.
   • Locate the entry corresponding to the DHCP server you wish to unauthorize.
   • Right-click on the entry and select Delete to remove the authorization.
5. Confirm and Close:
   • Confirm the deletion and close ADSI Edit.

Using Active Directory Sites and Services

1. Open Active Directory Sites and Services:
   • Open Active Directory Sites and Services from the Administrative Tools.
2. Enable Advanced Features:
   • Go to the View menu and select Show Services Node if it’s not already enabled.
3. Navigate to the DHCP Server Authorization Entry:
   • Expand Services, then NetServices.
   • Under NetServices, you will find entries for authorized DHCP servers.
4. Locate and Delete the DHCP Server Entry:
   • Right-click the DHCP server entry you want to unauthorize and select Delete.
5. Confirm and Exit:
   • Confirm the deletion to complete the unauthorization.

• Restart the DHCP Service: After unauthorizing the DHCP server, restart the DHCP service on the server to ensure it no longer leases IP addresses.

These steps allow you to unauthorize DHCP servers by directly modifying the AD configuration without relying on PowerShell or the DHCP Management Console.

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hth

Marcin