As we have seen in the previous recipe, a Lync resource forest requires a continuous synchronization between the accounts in the users' forests and the disabled accounts that must be provided in the forest in which Lync services exist. A directory synchronization product, such as Microsoft Forefront Identity Manager (FIM) 2010 R2, is a useful solution to transmit modifications from the user forests to the resource forest (for example, creating or deleting an account in the former one will automatically create or delete the disabled account in the latter). In the following schema, we can see a possible outline for a resource forest deployment with FIM (Identity Manager is not joined to the user and resource forest to show there is no need to insert it inside the existing forests):

This section will be dedicated to the configuration of FIM in a resource forest scenario.