This section provides guidance if you are deploying LRS in a multi-pool environment that includes Lync Server 2010 or Office Communications Server 2007 R2.
The User Replicator (UR) component in Lync Server gets user objects from Active Directory and places them into the Lync Server back-end SQL Server database. Only the UR in Lync Server 2013 is aware of LRS objects. The UR in previous versions of Lync Server and Office Communications Server do not detect the Active Directory attributes that designate LRS objects, and therefore was not aware of them.
If an LRS account tries to sign in to Lync, and performs autodiscovery based on SRV record or DNS A record look up, and if those accounts point to a previous version of Lync Server or Office Communications Server, LRS will receive a 404 Not Found response from the legacy pool. The legacy pool will not be able to redirect LRS to its Lync Server 2013 home pool.
You can address this problem with the following options: