Call waiting needs to be disabled on voice mail ports. When the Cisco Unity ports are called, they see the call waiting tone and drop the connection. The phones then display the Temporary Failure error message as if there was a network disruption.
The problem arises in new installations of Cisco CallManager 3.3(2) spB where call waiting for voice mail ports is set to default rather than to off. If the system setting for call waiting is set to true, then call waiting is enabled for voice mail ports.
Normally, voice mail ports are configured to roll over to the next port if busy, thereby hunting for a free voice mail port. To achieve a roll over configuration, configure each port to Forward Busy to the next port. If call waiting is configured, the call does not roll over to the next voice mail port right away, but rather effectively continues to ring until the Forward No Answer Timer expires. It takes 12 seconds (or x seconds depending on the setting of the Forward No Answer Timer) before rolling to the second port on Cisco Unity.
Because the voice mail ports are not set to roll over, the delay is not experienced. However, when the call waiting tone is detected on a voice mail port, the caller on call waiting is ignored. Eventually, the ports disconnect from Cisco CallManager, which is the symptom being experienced.
To resolve this issue, turn off the call waiting system wide by performing these steps:
Go to Service > Service Parameter and select Cisco CallManager Service.
Change the Call Waiting Enable Flag field from True to False.
Restart the Cisco CallManager service for the change to take effect.
Note: Turning off call waiting globally does not prevent the feature from being set up on a per-line basis. You can still set up call waiting on lines that need it by changing the Call Waiting drop-down list from Default to On.
To disable call waiting from the voice mail ports, run this script on Cisco CallManager:
@if "%2x" == "x" goto Usage
echo USE %2 >temp.sql
echo -- disable call waiting for numplan records associated with voice mail
echo Update NumPlan set tkStatus_CallWaitingEnable = 0 where pkid in >>temp.sql
echo (Select distinct M.fkNumPlan from DeviceNumPlanMap M, Device D >>temp.sql
echo where M.fkDevice = D.pkid and D.tkModel=80) >>temp.sql