Cisco Unity

Unity Mailbox Access Issues with Microsoft Exchange 2010 Load Balancer

Document ID: 116193

Updated: Jun 13, 2013

Contributed by Scott Hills, Cisco TAC Engineer.



This document describes a problem encountered during a troubleshoot of Cisco Unity and also provides a solution to the problem.


A Microsoft Exchange 2010 cluster has a Conditional Access Systems (CAS) load balancer in use. Unity has issues with the Message Waiting Indicator (MWI) or has issues with access to mailboxes. In order to troubleshoot further, you need to bypass the load balancer. However, due to production issues or other limitations, the load balancer cannot be removed.


As a workaround, you can modify the Unity registry in order to test a specific Exchange CAS server.

Note: Back up the registry before any change is made to the registry. Incorrect modifications to the registry might require a server rebuild. Perform a full Disaster Incident Response Team (DIRT) and/or Cisco Unified Backup and Restore Application Suite (COBRAS) backup of the server before any modification to the server is made.

  1. Open the command window.
  2. Enter the Regedit command.
  3. Navigate to HKLM\SOFTWARE\Active Voice\AvWM\1.00\.
  4. Create a new REG_SZ value, and enter the name CAS Server Override.
  5. Enter the value of the CAS server that you wish to point to as a fully qualified domain name (example:
  6. Exit the registry.
  7. Reboot the Unity server.
Updated: Jun 13, 2013
Document ID: 116193