At least three free IP addresses are needed to set up a HA pair.
For a one-armed configuration, only one interface is configured. Two individual Virtual IP (VIP) addresses are set on each LoadMaster unit as their physical IP address; one address for HA-1 and the other for HA-2. The third IP address is set for the shared IP address which is for the Web User Interface (WUI) management page and routing.
Additional addresses are needed if the customer wants to set up their HA pair as a two-arm configuration and configure more interfaces. Each additional interface configured will require three free IP addresses per interface.