Symptom

Caller continuously hears ringback tone while callee is able to hear caller. Only when the callee presses the Hold and Resume button 2 way audio is established.

Conditions

Call Flow PSTN----(VIC2-4FXO)GWY(29XX)----H323--CM(8.6.2.23047-2)--HTTP-ECC---Phone Issue Impact cu has workaround ie call works when MTP is invoked but when MTP is invoked Multicast MOH fails to work. Troubleshooting Performed ++ Issue not seen when call is made directly to the phone without being routed through ECC. ++ Using H323 Slow start or Fast start doesnot make a difference.

Workaround

When MTP is enabled on H323 GWY,there is no issue. HW:C2921 SW:c2900-universalk9-mz.SPA.151-3.T1 ======= Here is the engineering analysis: 1. On what version customer is facing the issue. [answer] c2900-universalk9-mz.SPA.151-3.T1 2. Trigger for this issue. [answer] This is a new setup. 3. Did they upgrade recently? [answer] No This issue only happens without MTP in CUCM and does not happen with MTP in CUCM. For the without MTP case, CUCM uses H245 to negotiate a new media to the CUCM-phone after connect. The later h245 negotiation seems triggering the ringback tone playing again. For thewith MTP case, there is no h245 negotiation since MTP media setup is there already for H323 GW so there is no issue of the with MTP case.

Further Problem Description