In a Layer 3 interface deployment and active/active
HA configuration, the firewalls are connected to routers, not switches.
The firewalls use dynamic routing protocols to determine the best
path (asymmetric route) and to load share between the HA pair. In
such a scenario, no floating IP addresses are necessary. If a link,
monitored path, or firewall fails, or if Bidirectional Forwarding
Detection (BFD) detects a link failure, the routing protocol (RIP,
OSPF, or BGP) handles the rerouting of traffic to the functioning
firewall. You configure each firewall interface with a unique IP
address. The IP addresses remain local to the firewall where they
are configured; they do not move between devices when a firewall
fails. See Use Case: Configure Active/Active HA with Route-Based Redundancy.