Consider the following scenario:
You have two Lync client users (user A and user B) who are in different subnets in a Microsoft Lync Server 2013 environment.
You configure the Location-Based Routing feature to restrict routing of public switched telephone network (PSTN) calls between Lync client users who are in different subnets.
User A receives a PSTN call. Then, user A tries to add user B into the call to create a meeting by using one of the following methods:
Clicks the telephone URI in user B’s contact card.
Rests the mouse on user B’s photo, then selects Lync Call in the drop-down list near the "Call" icon.
In this scenario, user A calls user B successfully, even though this should not be possible.
This issue occurs because Location-Based Routing only analyzes the location of the meeting organizer when a PSTN user is in the meeting.
To resolve this issue, install the following cumulative update:
2937310 August 2014 Cumulative Update 5.0.8308.738 for Lync Server 2013 (Front End Server and Edge Server)