Remove Rogue DHCP Authorized server from DHCP authorized list.

Some time we can see multiple DHCP server in the Manage Authorized Servers list of DHCP console, which is already removed from the domain. Before removing this make sure the IP address or server name is not present in AD or DNS. To remove this rogue DHCP server please follow the below steps.

1. Run the command to display the authorized server >netsh dhcp show server, then note the full FQDN server name and ip address and perform the following steps.
2. Type Net stop dhcpserver .
3. Netsh DHCP delete server Full server name IP address. Eg: C:\> netsh dhcp delete server Server-001.test.internal 192.168.0.10
4. Type Net start dhcpserver
5. Reboot the server and and check if it is displaying in the authorized list.

But if the old server still in the list then need to perform the below mentioned steps in Adsiedit:

1. Start Adsiedit.msc.
2. Right click ADSI Edit > click connect to > then select Configuration from select a well known naming context drop down list.
3. Expand the Configuration [Server Name] Container > then expand Services.
4. Select Net Services.
5. On the right hand side select record named CN=DHCPRoot.
6. Right Click the CN=DhcpRoot entry and then click Properties.
7. Highlight DhcpServers Attribute then click Edit button.
8. Highlight the entry with the rogue Domain name in the value box and click Remove. Click OK to close DHCPServers editors screen.
9. Once deleted the DHCPServers value will be displayed as not set.
10. Save the change by clicking OK and close Adsiedit.
11. Restart the DHCP server service.
12. Once you have restarted the DHCP Server service, run the following command: Netsh DHCP show server to confirm the old value is no longer displaying.