DSP channels on 2911 and DTMF issue

Unanswered Question
Jun 29th, 2010

Good afternoon Cisco Community,

I've a question about MTP resources and a DTMF issue. In fact, I installed two 2911 routers with both 64 channels. 32 channels are used for our E1 connected to the PSTN provider and 32 used for MTP purposes. Why? Because we have a SIP trunk between the CUCM and a Nortel CS 5.

As we are using MTP for transcoding purposes, I had to check the MTP required checkbox on the trunk. We have also a second trunk with Microsoft Exchange UM 2007 and here we are. This trunk uses the same Media Resource Group List than my Nortel Cisco trunk but I figured out that on the trunk with UM, we cannot use anymore the DTMFs for the authentication.

When I'm calling the UM VoiceMail, no entry is taken in consideration. I'm sure this has something to do with the hardware MTP resources because if I select on the CUCM <->UM Exchange an other Media Resource Group List with only the software MTP of the CUCM, the DTMF works again.

I've a workaround for the moment but I prefer using the hardware MTPs.

Any idea?

Best Regards,


I have this problem too.
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