Coexisting with Previous Versions

LDAP Ports and Protocols

By default, the server running ADC attempts to communicate with the Exchange directory bridgehead server on port 389 (379 for the Site Replication Service), which is the most commonly used Lightweight Directory Access Protocol (LDAP) port. Under some circumstances, you must configure the Connection Agreement for another port; for example, if Exchange 5.5 Server is deployed on a Windows 2000 domain controller. Active Directory components always start before the Exchange directory; therefore, the operating system locks port 389. The Exchange directory still starts, but LDAP communications are not possible. To work around this, use the Exchange 5.5 Administrator program to reconfigure the listening port for LDAP (usually, port 390 is a good choice), and then specify the port number on the Connection Agreement to match.

The Connection Agreement does not have any LDAP port configuration for Active Directory because it always attempts to communicate with Active Directory on port 3268. This is the reserved port for global catalog servers, which implicitly means that all Connection Agreements must be made into global catalog servers and not standard domain controllers.

Most communications that ADC establishes are based on LDAP; however, ADC uses a few synchronous remote procedure calls (RPCs) when you use Active Directory to create a User object but the mailbox is specified to exist on an Exchange 5.5 server. When the next replication cycle occurs, an instance of the mailbox object is created and a call is made to create new proxy addresses; for example, Simple Mail Transfer Protocol (SMTP), X.400, or Microsoft Mail addresses. The proxy address generator can be called only through RPC. This can be a consideration if a firewall exists between the server running ADC and the Exchange 5.5 bridgehead server.

Related Topics

Understanding Connection Agreements Specify an Alternative LDAP Port Number Set Up a Connection Agreement