Unless the LDAP Hostname resource attribute is set, the connector will perform a serverless bind to the directory. For the serverless bind to work, the connector server must be installed on a system that is in a domain and that “knows” about the domain/directory to be managed. All Windows domains managed by a connector must be part of the same forest. Managing domains across forest boundaries is unsupported. If you have multiple forests, install at least one connector server in each forest.
The LDAP Hostname resource attribute tells the connector to bind to a particular DNS hostname or IP address. This is the opposite of a serverless bind. However, the LDAP Hostname does not necessarily have to specify a specific domain controller. The DNS name of an AD domain can be used. If the connector's DNS server is configured to return multiple IP addresses for that DNS name, then one of them will be used for the directory bind. This avoids having to rely on a single domain controller.
Some operations, including pass-through authentication and before and after actions, require that the connector server be a member of a domain.