This document explains how to solve the problem when Cisco Unity voicemail does not recognize Dual Tone Multifrequency (DTMF) when calling the public switched telephone network (PSTN) for message notification.
There are no specific prerequisites for this document.
The information in this document applies to all versions of Cisco CallManager and Cisco Unity.
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When Cisco Unity calls a phone on the PSTN for message notification, it prompts the called party to enter information via DTMF. In some cases, Cisco Unity ignores the digits entered and acts as if there was no response. Though this symptom is with Cisco Unity, the problem is actually a faulty gateway configuration. In general, when this problem exists, calls from the PSTN to Cisco Unity correctly detect DTMF.
It is necessary that calls from the PSTN to Cisco Unity match on an outbound VoIP dial-peer, which should include the command dtmf-relay h245-alphanumeric. When calls from Cisco Unity to the PSTN go through the same gateway, if the extension configured on Cisco Unity's voicemail ports do not match the destination pattern in any VoIP dial-peer, then the gateway matches on dial-peer 0 instead. Dial-peer 0 is a hidden, default dial-peer, which does not have dtmf-relay enabled. In order to force the incoming VoIP call to match on an existing dial-peer, and to use dtmf-relay, add the command incoming called-number <#> to the dial-peer. In general, the dial-string referenced in this command is the same as the destination pattern from the pots dial-peer that makes up the other leg of the call. For example, if the pots dial-peer's destination pattern is 9T, the VoIP dial-peer's incoming called-number should be 9T.
dial-peer voice 1 pots destination-pattern 9T !--- The dial-string here is 9T. direct-inward-dial port 0/0:23 ! dial-peer voice 2 voip destination-pattern 4... incoming called-number 9T !--- This dial-string matches the pots dial-peer 9T. session target ipv4:10.100.25.2 dtmf-relay h245-alphanumeric
Note: If you use Media Gateway Control Protocol (MGCP) in the remote gateway, ensure that you have configured the mgcp dtmf-relay voip codec all mode out-of-band command under the dial-peer voice x voip command.
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