Any type of LDAP service, whether it is an actual server or a gateway to other LDAP services, is called an LDAP server. You can specify multiple directory services for high-availability failover protection.
Not every directory service in the list must be an LDAP server.
For example:
[DIRECTORY]
ldap=libsybdladp.so ldap://test:389/dc=sybase,dc=com ldap=libsybdldap.so ldap://huey:11389/dc=sybase,dc=com
In this example, if the connection to test:389 fails, the connection fails over to the DCE driver with the specified DIT base. If this also fails, a connection to the LDAP server on huey:11389 is attempted. Different vendors employ different DIT base formats.