The steps up until this point need to be done only once. The following steps are prerequisites that will need to be installed on every server in the Office Communications Server deployment (other than the domain controller and the SQL Server Back End server).
To install server prerequisites
Install the Microsoft Visual C++ 2008 Redistributable.
Install the Microsoft .NET Framework 3.5 SP1.
A restart will be required at this point.
Install the SQL Server Native Client.
Install Office Communications Server 2007 R2 Core Components. This file is located in the Setup folder.
Install Unified Communications Managed API 2.0 Redistributable. This file is located in the Setup folder.