Which method does a Cisco Unified 9971 phone use to send keep-alive messages to Cisco Unified
Communications Manager?
A.
SIP NOTIFY with Event set to keep-alive
B.
SIP OPTIONS
C.
SIP REGISTER with Expires set to zero
D.
SCCP StationRegister
E.
SCCP StationServerReq
Explanation:
Phone registers with primary and establishes keepalive connection with secondary.
Expires = 0 keepalive mechanism allows Cisco SIP Phones to more closely resemble the failover /
fallback behavior of SCCP.