Consider the following scenario:
You have multiple users who are enabled for the remote call control (RCC) and multiple users who are enabled for Enterprise Voice in a Microsoft Lync Server 2013 environment.
All the Enterprise Voice-enabled users are configured to have the same main telephone number and different extensions.
An RCC-enabled user tries to call an Enterprise Voice-enabled user.
In this scenario, the caller can hear ring-back tone. However, the callee does not see an incoming call notification in a client for Lync nor does he hear desk telephone ringing. Additionally, an ambiguous 485 error is logged in the UCCAPI logs.
This issue occurs because the extension number of an Enterprise Voice-enabled user is parsed incorrectly when an RCC-enabled user calls the Enterprise Voice-enabled user.
To resolve this issue, install the following cumulative update:
2905048 Description of the cumulative update 5.0.8308.577 for Lync Server 2013 (Front End Server and Edge Server): January 2014