An administrator is configuring a new Cisco UCM with PSTN capabilities. Due to bandwidth constraints, audio compression is used on the codec. DTMF must work as expected because the customer is…

Question

Options

• Ain the DTMF setting under SIP profile on the Cisco Unified Border Element
• Bin DTMF settings in the audio codec preference list under regions in the Cisco UCM
• Cin regions on the Cisco UCM where you set the appropriate codec to use
• Din the dial peer on the Cisco IOS router

• A
  4% (1)
• B
  11% (3)
• C
  7% (2)
• D
  78% (21)

Explanation

When a compressed codec like G.729 is used, DTMF tones cannot be reliably transmitted in-band because the codec's compression distorts the tones. Out-of-band DTMF relay must be used instead (e.g., RFC 2833 / RTP-NTE or SIP INFO). On a Cisco IOS router or gateway acting as a SIP gateway, out-of-band DTMF relay is configured under the dial peer using commands such as 'dtmf-relay rtp-nte' or 'dtmf-relay sip-info'. UCM regions (Options B and C) control codec selection, not DTMF method. The SIP profile on a Cisco UBE (Option A) can also carry DTMF settings, but the primary and most direct configuration point for a standard SIP-based IOS gateway is the dial peer - making D the correct answer for this scenario.

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