D-Link ShareCenter DNS-320L User Manual page 434

Section 5 - Knowledge Base
Under Mode, select Master from the drop-down list and then
click Add.
Enter the IP address of the other UPS slave on the network.
Click the + button to add more IP addresses.
Make sure the DNS-320L and the UPS slaves are on the same
physical network.
DNS-320L 428
D-Link ShareCenter™ User Manual