Assume that you use Microsoft Lync Server 2013 Planning Tool to plan a Lync Server 2013 environment that needs to be a high availability solution for a few users. For example, you plan the environment for 1000 users. In this situation, Lync Server 2013 Planning Tool recommends that you deploy an Enterprise Edition Front End pool that employs two Front End Servers.
Note The best practice is that you deploy an Enterprise Edition Front End pool with three Front End Servers.
To resolve this issue, install the following cumulative update:
2846490 Description of the cumulative update 5.0.8308.420 for Lync Server 2013, Planning Tool: July 2013
For more information about the topologies and components for Front End Servers, Instant Messaging, and Presence, go to the following Microsoft website: