ringback tone issue with blind transfer

[Liran Farazis]

We are facing a problem with ringback tone not being played when performing blind transfer.

PSTN -- PRI --CISCO router -- sip trunk to cucm -- CUCM -- sip phone 

customer call from the PSTN and the call is being answered at the ip phone ,press trasnfer, moh is being played to the phone over PSTN and after finish to dial the transferred number I push on transfer again.

the PSTN customer is hearing silent until the transferred number is answering.

when I check MTP on the sip trunk at the cucm we can hear the ringback but I don't want to involve MTP on every call.

cucm version 10.5.2su2 

ip phone 7962 

iOS version 15.0(1r)M16

do you have any idea what can cause this issue?

Thanks a lot

[Leszek Wojnarski]

Hi Liran,

Do you have MRGL assigned to your SIP trunk. This MRGL needs to contains ANN and in region setting you'd need to allow codec that you use on IPVMS service (by default it uses 711 only).

If all that is good, then you can publish CUCM Call Manager, and IPVMS traces for the analyze.

Leszek