Consider the following scenario:
You have several Active Directory sites in a Microsoft Lync Server 2013 environment.
You configure Location-Based Routing for each site and deploy Enterprise Voice in the environment.
An external network is set up by using a private subnet. The IP addresses of the subnet are in the IP address range of the AD sites.
A user tries to make a call to connect to a front-end server that is in the Lync Server 2013 environment from the external network.
In this scenario, the call is routed incorrectly based on Location-Based Routing that is configured for the AD sites.
This issue occurs because an external client that has an IP address which is in the IP address range of the AD sites is identified as an internal client.
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