A high-availability (HA) pair configuration uses only the hardwire serial cable connection to determine
device state. A power outage occurs to the PDU powering the active unit. The standby unit takes over the
active role as expected.
How is the peer unit able to determine the active unit is unavailable?

A.
voltage loss on serial cable

B.
no data stream received on serial port

C.
no response on management interface

D.
no heartbeat packets received on self IPs