A Secondary IP Set is a set of one or more master name server IP addresses for a secondary DNS domain. In order to delete an IP Set from the system, you must remove the IP set from any secondary DNS domains prior to deleting it.
Step 1: Select the Advanced menu and click on “Secondary IP Sets”
Step 2: Select an IP Set to remove by clicking on a row. Then click the Trash icon.
Step 3: Click Delete to confirm the removal.