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Problem with answering machines and PSTN voice mails


We are experiencing issues when we place a call to the PSTN and it is redirected to a answering machine, for example if I place a call to my cell phone and it is powered off normally it will be  answered by the voice mail of my celular company, but in this case whe have two strange behaviors:

1.- the call keeps ringing like my cell phone were available.

2.- the call is connected but we are experiencing something like one way audio, we cannot hear audio from the voicemail, but checking my voice mail on my cell phone I realized that I am able to leave a message.

This two issues occours randomly and for both home answering machines and cell phones voicemails, with regular calls we have no problems.

we have:

     CUCM 9.1

     GW 3900 - 15.1 (4) M7

The GW is connected with the CUCM via SIP, and with the PSTN with E1 R2.

Here is part of the configuration that I think could be relevant:



voice call convert-discpi-to-prog


voice service voip

no ip address trusted authenticate

allow-connections sip to sip

signaling forward unconditional


  bind control source-interface Loopback0

  bind media source-interface Loopback0

  rel1xx disable

  min-se 360 session-expires 360



voice rtp send-recv


controller E1 3/1

framing NO-CRC4

line-termination 75-ohm

ds0-group 0 timeslots 1-15,17-31 type r2-digital r2-compelled ani

cas-custom 0

   country telmex

   release-guard-time 2


   category 2

   answer-signal group-b 1

   ani-digits min 4 max 20

   answer-guard-time 500

   timer interdigit incoming 1000


   dtmf timer inter-digit 250

description E1 para PSTN


voice-port 3/1:0

cptone MX


dial-peer voice 401 pots

  description ** LLAMADAS A CELULAR LOCAL  y LD**

  preference 1

  destination-pattern 9044..........

  port 3/1:0

  forward-digits 13

  no register e164


New Member

Problem with answering machines and PSTN voice mails

Hi Sergio

What debugs have you cheked?


César C.

Problem with answering machines and PSTN voice mails

Hi Cesar,

I've  reviewed "debug voice ccapi inout" and "show call history voice", but I found anything, I attached both files.

Best Regards!

New Member

Problem with answering machines and PSTN voice mails


Can you please post both the output of a debug ccsip message and a deb isdnq931 while calling to a switched off mobile phone?