Implementing and Operating Cisco Collaboration Core Technologies (CLCOR) — Question 220

An administrator uses the Cisco Unified Real-Time Monitoring Tool to investigate recent calls on a Cisco UCM cluster. The SIP trace for an on-net, direct-media call shows two 180 Ringing and two 11 BYE messages. Why are there multiples of each message type in the trace?

Answer options

• A. The source phone sends a 180 Ringing signal to the Cisco UCM, which sends a 180 Ringing signal to the destination phone. The same process applies to 11 BYE messages.
• B. The source phone must signal to the destination phone that it is ringing, and the destination phone signals back with a 180 Ringing message. The same process applies to 11 BYE messages.
• C. The destination phone signals back to the Cisco UCM that it is ringing, and the Cisco UCM signals back to the source phone.
• D. The calls have an MTP in the call path due to different codec support. The calls are subsequently split into two call legs.

Correct answer: C

Explanation

The correct answer is C because it accurately describes the signaling flow where the destination phone informs the Cisco UCM of its ringing status, which is then communicated back to the source phone. Options A and B incorrectly imply that the messages are directly exchanged between the phones without involving the Cisco UCM, while option D introduces an irrelevant detail about MTP and codec support that does not pertain to the message counts.