Recently I’ve seen this topic popping up more often in the TechNet forums and decided to try it myself. I ran through the install in a fresh lab with Windows 2008 Active Directory (2003 Forest functional level and 2008 Domain functional level) and a single Windows 2003 SP2 Member Server.
I had read some posts where people were running into problems performing the initial Schema/Forest/Domain prep steps, and they seemed to fall into two categories: executing the setup on the wrong computer or some type of port connectivity issues between servers. First off, Windows Server 2008 is NOT a supported host operating system for Office Communications Server 2007, as outlined in the OCS 2007 Supportability Guide. Also notice that OCS 2007 is specifically listed in the "Applications that are incompatible" section of knowledge base article KB948680. So any attempt to run the setup wizard on a Windows 2008 server (as in the domain controller) will fail. As long as there are no LDAP connectivity issues between servers, the setup wizard should be able to make all Active Directory changes when executed from a Windows 2003 server in the domain, assuming sufficient rights are granted.
To test this I simply added my domain administrator account to the root-level Schema Admins group and successfully prepped the schema, forest, and root domain using the setup wizard on the Windows 2003 Member Server. But if for some reason this doesn’t work or the steps need to be performed locally on a domain controller, then you can use the LCSCmd.exe to Prepare Active Directory.
LCSCmd.exe /Forest:contoso.com /Action:SchemaPrep
LCSCmd.exe /Forest:contoso.com /Action:ForestPrep
LCSCmd.exe /Domain:contoso.com /Action:DomainPrep
Take note that this applies to a fresh installation of Communications Server in an existing Windows 2008 domain. When planning to upgrade a Windows 2003 Active Directory forest/domain which is already running OCS, be aware that upgrading any domain controllers to 2008 will break OCS. The forest prep command will need to be reissued after the upgrade in order to re-establish the lost functionality.
LCSCmd.exe /Forest:contoso.com /Action:ForestPrep
Obviously the Active Directory Users and Computers snap-in on the domain controllers will not contain the Communications Server tab or the tasks to enable user for OCS, so administration should be performed from the OCS server itself or another supported host.
