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