XCON: Multiple X.400 Connectors Between Two Exchange Server Computers

If you install multiple X.400 Connectors between two Exchange Server computers (in different sites), using the TCP stack, each server requires multiple host names or multiple IP addresses. Each X.400 Connector needs a unique IP address or Host name entered under Address Attribute on the Stack tab of the X.400 Connector properties page.

If multiple X.400 Connectors are set up to the same host or IP address, the Event Log shows consistent socket errors and no connector works. The Exchange Server TCP stack has problems determining which connector is requesting a connection to the message transfer agent (MTA). By adding a second IP address to the server TCP/IP settings (each server), or a second host name to the LMHOSTS file, each connector then has its own TCP/IP connection to the remote server.

The reason is that the local T,S,P Selector values are associated with the Stack, and not the connector. Each X.400 Connector on a single server that uses the TCP transport must use the same TCP stack, therefore, the same Stack values apply. The second IP address or Host name gives each connector a unique identifier to the remote stack.

Note that the above applies to Exchange Server 4.0 and 5.0. Exchange 5.5 SP1 now accomodates creating multiple X.400 Connectors on the same IP address. For additional information, click the article number below to view the article in the Microsoft Knowledge Base: