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.
Technical Tips Conventions for more information on document
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
!--- The dial-string here is 9T.
dial-peer voice 2 voip
incoming called-number 9T
!--- This dial-string matches the pots dial-peer 9T.
session target ipv4:10.100.25.2
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.