300-070 Question #57: Real Exam Question with Answer & Explanation

The correct answer is C: 10.100.4.65. A SIP Back-to-Back User Agent (B2BUA) sits in the middle of a SIP call, terminating the incoming SIP dialog from one endpoint and independently originating a new SIP dialog toward the other endpoint. Unlike a SIP proxy (which forwards messages), a B2BUA maintains full control of

Question

Refer to the exhibit. Which party has a SIP B2BUA role in the call?

Exhibit

Options

A172.17.4.100
B10.100.4.65 and 172.17.4.100
C10.100.4.65
DNone of the parties has a B2BUA role in the call.
E10.100.4.68 and 10.100.4.65

Explanation

A SIP Back-to-Back User Agent (B2BUA) sits in the middle of a SIP call, terminating the incoming SIP dialog from one endpoint and independently originating a new SIP dialog toward the other endpoint. Unlike a SIP proxy (which forwards messages), a B2BUA maintains full control of both call legs. In this scenario, 10.100.4.65 is Cisco Unified Communications Manager, which always operates as a B2BUA - it terminates the SIP call from the originating device and establishes a separate SIP call toward the destination. The other IP addresses are endpoints, not B2BUAs.

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