Showing results for 
Search instead for 
Did you mean: 

Conferencing attempt suddenly reboots the phone



We recently deployed a ISR4321 w/UC License (UCME) at a customer where they have about 16 extensions and a 30 channel SIP trunk from the ISP. 


We configured the entire system and everything works fine except outbound conference calls. 

When we try to call multiple extensions & do a conference - it works without much of an issue. 

However, the trouble starts when we try to call an outbound number and press the conference button on the phone. We have L-CME x 16 licenses & L-CUBE x 30 licenses for this installation.  


When we try to call the outbound number - the phone hangs & reboots itself. 


What are we doing wrong? We were told that PVDM card is not required in case of a pure SIP Trunk installation. And we definitely don't have any budget left for buying a PVDM... in case it is required. 

Jaime Valencia
Hall of Fame Cisco Employee

A PVDM is not mandatory, but that doesn't mean a particular scenario will not need one. A reputable consultant or a Cisco partner with voice specializations should have been tasked with the design of the system, and then they would take into account the needs based on your requirements to determine whether a PVDM would be needed or not.

If you're using different codecs for example, that's a case in which you would need a PVDM as software based conferencing is limited to G711. A HW conference using PVDM can mix multiple codecs for a conference.


I would start by making sure conferencing was properly configured, and review the limitations of software based conferencing to make sure those actually meet your needs. Refer to the CME administration guide for all the configuration and details on conferencing.


If it's properly configured, then review debugs for that call in which you're trying to conference an external party to understand what happens with the call, and maybe logs from the device as the next step.



if this helps, please rate
Recognize Your Peers
Content for Community-Ad