Callers inform you that they hear a second dial tone after dialing the number 4085550123. Which dial-peer configuration command resolves this issue?
A. answer-address 408555….
B. destination-pattern 91[2-9]..[2-9]…..
C. forward-digits all
D. direct-inward-dial
correct answer is
D. direct-inward-dial
D is the answer
When a voice call comes into the Cisco IOS router/gateway, the voice port on the router is seized inbound by a PBX or CO switch. The router/gateway then presents a dial tone to the caller and collects digits until it can identify an outbound dial peer. Whether the digits are dialed with irregular intervals by humans or in a regular fashion by telephony equipment sending the pre-collected digits, dial-peer matching is done digit-by-digit. This means the router/gateway attempts to match a dial peer after each digit is received. This process is called two-stage dialing.
However, if the PBX or CO switch sends a setup message containing “all” the digits necessary to fully route the call, those digits can be mapped to an outbound Voice-Network dial-peer directly. With DID, the router/gateway does not present a dial tone to the caller and does not collect digits. It forwards the call directly to the configured destination. This is called one-stage dialing.
https://www.cisco.com/c/en/us/support/docs/voice/digital-ccs/14072-direct-inward-dial.html
D https://supportforums.cisco.com/document/16911/how-stop-cisco-ios-gateway-sending-second-dial-tone-call-through-isdn-pri