Run the following command:
net config <interface-name> <IP address> netmask <netmask>
type floating
The net config command with the float option is the only way to configure a
floating IP address. There is no method available in Data Domain System
Manager to configure a floating IP address.
net config eth4a 2.2.2.1 netmask 255.255.255.0 type floating
Configure System For Use
92 Data Domain DD9500 and DD9800 Systems 6.1 Hardware Overview and Installation Guide