Dropped Voicemail Messages


I have a UCM6510 with SIP Trunks for a large medical office. Customer has been reporting dropped voicemail messages since October. We have listened to the messages, and they are in the middle of a sentence and it drops the message. We have the voicemail messages set to allow 15 min of recording of message. Minimum message is 3 sec. RTP Keep Alive is set to 10 seconds under TOS. This is happening on multiple mailboxes.
Since it is a medical office, they do not have voicemail to email set up. so it stays on the phone.
We have upgraded multiple times, now at the latest of We have factory defaulted the system and reloaded the database. We have changed out the hardware.
Have tried to work with Grandstream and cannot get a capture of when it is happening. It is not every voicemail or the same mailbox. Any suggestions is much appreciated


Time the messages that drop and see if any commonality. You might also contact the provider and provide them with the number, date& time and see if they can review the trace and provide the flow so you can see what side ended the call.


The messages are shorter than what the CDR and the provider show. Provider show goodbye from caller.
There have not been people calling back saying that they got hung up on.
The message time is not consistent and it is on multiple mailboxes
And it doesn’t do it all the time, and different mailboxes, different phones. When the call drops, the voicemail acts like the message was ended.
Working with Grandstream later today again


If the provider is indicating the disconnect is coming from the “caller”, as stated, then it does not appear to be UCM issue unless the RTP keep alives are not handling doing as they should. Given the randomness of when the call drops this seems unlikely, buy I suppose not impossible. The UCM is the callee in this case.

The provider should be able to provide the trace of such a call so that you can identify it as being a call that was indeed of interest and impacted and that the allegation is true. Trust but verify if you can.

Given the October time-frame it does not appear to be a FW issue as I suspect many others would have the same issue to include my 6510 clients.

You might think about adding a different provider as a test and forwarding (not porting) some numbers from the current to the new provider as perhaps this may expose more of the issue. In the meantime see if you can find any similarities in the dropped calls - cell phone? Carrier? Area code, exchange? You may need to ask the carrier to look upstream to see if they can identify why.