A storage unit is uniquely identified by a combination of the IP address of processor card 1, the IP address of processor card 2, and the storage unit machine type and serial number. You cannot have two storage units with identical values for one of those three parameters. You have attempted to enter an IP address for processor card 1 that is already in use.
Enter the correct IP address for processor card 1. Verify that you have entered the correct IP address for processor card 2 and the correct machine type and machine serial number, and resubmit the task.