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sip call drops

Hi guys. we are having some sporadic issues when users calls drops on  international call by using our sip trunk.  At the same time i am getting alerts MediaList exhausted on the same MRGL which users use . 

I don't have users phone number yet to trace calls, waiting them from servicedesk . Is that medialist exhausted may causing call drops? 

-in case if sip trunk has no Media Termination port required 

-in case if sip trunk has Media Termination port required checked.

Thank you 

Cisco Employee

Hi Bekzod,

If the MTP resource is being requested in the call ( whether MTP is checked or not ) the MRGL should have an MTP to offer. You may check if all the MTP resources are registered properly and specially if this issue is being see during peak hours then it could be due to lack of adequate number of MTP resources. For IOS based MTP you may try increasing the number of sessions on the MTP config on the gateway. Some CUCM versions also are suspect to MTP leak issues where MTP once allocated is not deallocated at end of the call, but that can be determined via traces and the CUCM version in use.




Thank you for response.  SO MTP lack can cause this call drops . CUCM is 10.5 . I saw sdl trace of calls which was dropped, I see cancel coming from user side, user dialed 10 times and every times cancel coming from user side. User (senior vice president )says call drops when it just connects .  It was during high  peak hours time. I tested few hours later from that phone 2 times no drops. 

Can you please share how to troubleshoot MTP/media resources ? 


Also I am trying to understand if I have this path :


and MTP req checked on sip trunk between CUCM and PBX and no MTP req  btw CUCM and CUBE , when phone is dialing to PSTN (as I remember MTP is inserted for every outbound call) for CUCM its incoming call but then its kinda outgoing but on sip trunk which has no MTP required .... 

Will be MTP inserted at this case ?


So how CUCM works it treats it as two separate call leg.

So its can't insert MTP if there is no MRGL associated with the device pool or SIP trunk on the second call leg.

Ideally even if the MTP required is not checked, but you have an MRGL assigned with MTP Resource, CUCM should be able to pick the resource on a need basis.




the thing is 1st sip trunk has different mrgl than second sip trunks device pool .  That's why I am trying to understand if its incoming call for CUCM or outgoing and which mrgl will be used. 

Also I dont see that FailedtoAllocateMTP message on CM trace I downloaded from RTMT .  Am I looking into correct place trace ?


You can check the "When do I need an MTP??" section of the following wiki page

Additionally, the trace for the failed call will also contain an MTP allocation request and a response of something like FailedToAllocateMTP  if the call indeed fails due to lack of MTP resource. You can filter the Media resource Manager messages to check this MTP request and allocation.