Cisco Unity Connection

Unity Connection Single Inbox Load Balancer Issue

Document ID: 116455

Updated: Sep 04, 2013

Contributed by Scott Hills, Cisco TAC Engineer.



This document describes a problem encountered with Load Balancers and the Cisco Unity Connection Single Inbox feature. Often this issue is caused when the Sticky Connection feature is not used. Essentially, you want the same Exchange Web Service (EWS) connection used throughout the same transaction. This document provides a specific example of an issue seen with a Load Balancer in use.


Messages for different users do not consistenly sync to Microsoft Exchange 2010. This means that there are times when messages for the same users sync properly without any change.

In the case described here, a Cisco Application Control Engine (ACE) Hardware Load Balancer is in use. The CuMbxSync trace might show this error at the moment of failure:

HTTP request failed with error:
 Failed sending data to the peer --
SSL read: error:00000000:lib(0):func(0):
 reason(0), errno 104, HTTP status code: 0

A packet capture might indicate an EWS connection from Cisco Unity Connection to Microsoft Exchange that resets. The reset might be caused by the Load Balancer.


The Load Balancer uses a policy that is designed for Microsoft Outlook Web Application (OWA), and it resets connections frequently. In order to resolve the issue, you must create another virtual IP on the Load Balancer that is also used in order to connect to the Microsoft Exchange Client Access Server (CAS), but is not processed through the OWA policy that applies the Sticky Connection based on session cookies. Then, point Cisco Unity Connection Unified Messaging Service to this virtual IP address, and apply it to the user.

In order to implement this solution, complete these steps:

  1. Set up a new Unified Messaging service that points directly to the CAS, not the Load Balancer. In this case, you might see that messages are always delivered, and you do not see the intermittent failures. This verifies that the Load Balancer causes the problem.
  2. Navigate to Unified Messaging > Unfied Messaging Service > Add New, and enter the appropriate information. Point directly to the Microsoft Exchange CAS fully qualified domain name or IP address.
  3. Navigate to Users > (select user that you want to test with) > Edit > Unified Messaging Accounts, and delete the current account, if one exists. Then add the new service that you created.
Updated: Sep 04, 2013
Document ID: 116455