With Cisco ASA active/standby failover, what is needed to enable subsecond failover?

With Cisco ASA active/standby failover, what is needed to enable subsecond failover?

A.
Use redundant interfaces.

B.
Enable the stateful failover interface between the primary and secondary Cisco ASA.

C.
Decrease the default unit failover polltime to 300 msec and the unit failover holdtime to 900 msec.

D.
Decrease the default number of monitored interfaces to 1.