Firepower HA Standby Interfaces show unassigned

[Scott_22]

I've noticed that unlike with ASA, the FTD appliances are not configured with a standby IP when the interfaces are configured. Instead, the secondary peer interfaces show as unassigned. Just to wrap my head around this - when the appliances fail over, the IPs are taken over by the secondary peer and it begins answering arp requests for them? 

[Marvin Rhoads · Accepted solution]

Just like with ASA, you can optionally assign standby IP addresses to interfaces in an HA pair.

Either way, the newly active unit will send a gratuitous ARP when it takes over the active role so that the adjacent upstream and downstream devices recognize it as the "owner" of the active IP addresses.

[Scott_22]

Is there an advantage to adding the standby IP address over using only the single IP? Does it aid in the fail-over time when the peers fail-over between one another?