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SIP Phone failover FAQ

The following are some frequently asked questions on SIP Phone failover.

Q1. How does Call Manager know that the SIP  phone becomes un-reachable?

A: Cisco Unified Communications Manager knows that the phone is unreachable when cucm tries  to send some message to phone and it gets tcp connection failure, or cucm  does not receive re-REGISTER message.

Q2. How does the sip phone know that  CallManager becomes un-reachable and starts to failover?

A: SIP Phone knows that CUCM is unreachable when phone tries to send some message to cucm and get tcp connection failure and start failover process.

Q3. Is geometric timers applicable to Cisco SIP IP  phones?

A:Yes, geometric timers are applicable to Cisco SIP IP  phones.