Single floating IP address(also known as a floating IP or shared IP) is supported only in anactive/passiveHA pair. In active/active HA, both firewalls are forwarding traffic simultaneously and thus do not share a single floating IP.
"In active/passive HA, a single floating IP address is used for seamless failover. Active/active HA requires separate IP addresses and does not support a single floating IP." (Source: Active/Passive vs. Active/Active HA) Thissimplifies failoverin active/passive deployments by using a single shared IP that moves to the active peer upon failover.