Symptoms
Cannot delete an IP pool due to the following error: "IP pool "Test Pool" can not be deleted. Set of IP addresses from the pool are used."
Cause
The IP addresses from the pool you are trying to delete are needed to provide customer services.
Resolution
Navigate to the Customer services tab of the properties of the Hardware Node (or VPS) that the pool in question is assigned to. Delete all customer services that are using IP addresses included in that pool, as shown in the following screenshot: