The specified IP address or hardware address is being used by another client

I’ve just run into another DHCP issue that I would like to share with you. Once I have tried to edit existing DHCP reservation from an active scope I got this error message:

The specified IP address or hardware address is being used by another client.

After this I have tried to delete the reservation for this client. Even after the deletion I was unable to create a new reservation for this client. I have obviously forgot one crucial step :). Since we’re using DHCP with 2 failover partners I had to replicate the scope after deleting the reservation for the client.

After Scope replication I was able to create new reservation for the client. But, that was not the end of DHCP problems.

Once I tried do delete a lease I have received another error message:

The following error occured while deleted the record (ip address)
An error occurred while accessing the DHCP database. Look at the DHCP server event log for more information on this error.

In order to fix this error you’ll have to right-click on the DHCP scope, click Reconcile.
In a pop-up window click Verify and once Scope records appear click on Reconcile.

This procedure will compare and reconcile scope information from the database with registry.