Hi, I have discovered this issue in my lab test environment too, but my SW MTP on CUCM gets invoked automatically when my SIP EX90 VTC, which uses RFC2833, makes successful calls over my MGCP GWY w/PRI. The audio calls work fine, but the media flows from EX90 through the CUCM vs directly from EX90 EUD to the MGCP GWY. Since Cisco 7975 phones support both In-Band and OOB DTMF, there is no such problem. Phones work great. No DTMF mismatch.
I don't want to use the SW MTP on CUCM, nor do I want to build a IOS HW or SW MTP on the GWY. Therefore, I experimented with MGCP NSE, NTE-CA and NTE-GW since they support In Band DTMF. However the RTP Payload types need to be manually configured since they are not actually RFC2833 compliant. I have looked online to see if there is a proven solution, but no luck so far.
I'm not working this effort full time, so I haven't completed working the problem. I'm hoping I can set the MGCP RTP payload-type value to match the RTP payload type and finally get the MGCP GWY to support In Band DTMF. If I can get that working, I can resolve the issue of having the SRTP media flow through a MTP. This will be a more efficient flow.
Oh, almost forgot, the EX90 audio call works fine, but when the EX90 calls my remote CFB on the other side of the MGCP GWY, the DTMF digits fail to reach the CFB. PIN Code fails. I haven't had time to sniff the packets yet, but I assume the MTP is being envoked just like it is on my other cluster, which I have used wire shark to capture the EX90 to CUCM/MTP flow. I thought the DTMF should have been converted by the CUCM MTP since the media is flowing through the CUCM MTP. Weird.
Thoughts?
