Unable to route video calls over SIP trunk using MTP

[Joseph Chirayath]

Hi,

My requirement is to have the same SIP trunk to do both audio calls from the gateway to WebEx through VCS and video calls from the telepresence room to WebEx again using the same route through VCS. The call flow is starting from the call manager and then going in through the SIP trunk to VCS Expressway and then connecting to Cisco WebEx.

When I am enabling require MTP on the trunk DTMF tones for the calls coming from the voice gateway works but the video calls from the telepresence using the same trunk goes to an audio only call WITHOUT VIDEO. When I uncheck MTP on the trunk video call from the telepresence works but the DTMF tones STOPS getting relayed from the voice gateway to the SIP trunk to WebEx and the telepresence unit is able to make video calls out to WebEx.

I tried using IOS MTP and configuring the codec pass through and applied it to the trunk and the telepresence unit then enabled MTP on the trunk to see if it works but unfortunately ended up with the same result.

Kindly reach out to me if you need any further information.

Your input is much appreciated.

Regards,

Joseph.

[Nick Halbert-Lillyman · Accepted solution]

Hi Joseph,

A few things you could try;

1. Change the DTMF profile on the SIP trunk to VCS

2. On the SIP profile for the trunk to VCS, try enabling Early Offer "Best Effort - insert MTP if required" and ensure the trunk has a media resource group list with some MTPs in it

3. If you are using numeric dialling from audio and SIP route patterns for video, try configuring a second trunk to VCS on a different SIP port and a corresponding neighbour zone (you will need to make a new SIP trunk security profile to change the port on the CUCM end).  Route the numeric/audio only calls via the MTP trunk and have your SIP route pattern point to the trunk without MTP required

[Joseph Chirayath]

Hi Nick,

Change the DTMF profile on the SIP trunk to VCS, I changed the DTMF signaling method to OOB and RFC 2833 which worked. I had tried enabling Early Offer "Best Effort - insert MTP if required" in the past but did not work.

Thank you for the input.

Regards,

Joseph.