IP WAN failure has occurred. Which two configurations must be made to allow calls to or from an IP phone at a branch location to complete to a destination outside of that branch? (Choose two.)

Question

Options

• ASurvivable Remote Site Telephony is configured on the branch router.
• BLAN failover configuration is set to Survivable Remote Site Telephony.
• CCall Forward UnRegistered option is configured on each branch phone profile.
• DPOTS WAN failover is set to Survivable Remote Site Telephony.
• EAn ISDN is configured as a primary survivable backup site

• A
  79% (22)
• B
  4% (1)
• D
  7% (2)
• E
  11% (3)

Explanation

When a WAN link fails at a branch, IP phones lose registration with Cisco Unified Communications Manager (CUCM) at the central site. Two configurations work together to maintain call continuity:

A. Survivable Remote Site Telephony (SRST) on the branch router: SRST is a Cisco IOS feature that allows the branch router to act as a fallback call agent. When phones detect loss of connectivity to CUCM, they re-register with the SRST router, which can then route calls locally via PSTN. Without SRST configured on the router, there is no fallback call processing agent at the branch.

C. Call Forward UnRegistered (CFUR) on each branch phone profile: CFUR is a CUCM setting that specifies where to forward calls destined for a phone when that phone is unregistered (i.e., when the WAN fails). This ensures that inbound calls from outside the branch - which still arrive at CUCM - are redirected to a reachable destination (such as a PSTN number or voicemail) rather than failing. Together, SRST handles outbound calls from unregistered phones, while CFUR handles inbound calls to those phones.

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