Resolution
In order to avoid forwarding loops in Cisco Unity, use these features in the Advanced Setting tool:
- System - Reject Forwarded Notification DTMF Tone
This setting defines the 4th-column DTMF tone (A, B, C, D) that Cisco Unity uses in order to detect forwarded message notification calls so that they can be rejected and not answered, which prevents an endless loop.
If a user turns on message notification and sends message notification calls to a device that in turn automatically forwards to Cisco Unity when calls are not answered, Cisco Unity detects that the forwarded call was originally sent by Cisco Unity as a message notification and does not answer it. Because the caller ID of the original notification call can be lost, Cisco Unity detects message notification calls that are forwarded back with the 4th-column DTMF tone that is specified in this registry key located at:
HKEY_LOCAL_MACHINE\Software\Active Voice\MIU\1.0\Initialization\DetectionTones
The key name is RejectForwardNotification.
These are the possible values:
The recommended value is A. Avoid the C value, because it can conflict with AMIS calls.
In order to disable Reject Forwarded Notification, choose (disable) from the drop-down list.
System - Reject Forwarded Notification Guard Time
This setting defines the guard time in milliseconds that Cisco Unity uses for the Reject Forwarded Notifications DTMF Tone setting.
The guard time is the length of time in milliseconds that Cisco Unity listens for a 4th-column DTMF tone in order to determine whether the call is a message notification that is forwarded back.
The location of the key is:
HKEY_LOCAL_MACHINE\Software\Active Voice\MIU\1.0\Initialization\DetectionTones
The key name is RejectForwardNotificationGuardTime, and it is a DWORD key.
The value must be greater than 0. The recommended setting is 3000 ms.
For more information Cisco Unity Troubleshooting Guide and Cisco Unity Maintenance Guide.
