Migrating to Exchange 2000 with Global Catalog Server on Exchange 5.5
Hi, Scott. I'm in the process of migrating to Windows 2000 and Exchange 2000. I had an NT domain with one PDC and a BDC. I upgraded the PDC (also the Exchange Server) to Windows 2000, so I have a Windows 2000 Domain Controller with Exchange 5.5. The plan was to install Win2000/Exchange 2000 on another machine. However, I came across the Microsoft article Q275127. It says: "There is no supported migration path to Exchange 2000 while the Exchange 5.5 installation exists on a Global Catalog Server." The article implies that there is no way forward for me. Is this true?
What the article says is true. Microsoft does not support running Exchange 5.5 on a global catalog server because port conflicts occur between the Exchange 5.5 directory service and the Name Service Provider Interface.
However, that does not mean you cannot move forward. What you'll want to do is to bring up a new Windows 2000 DC on a separate machine, promote it to a GC server, and then demote your existing Exchange 5.5/DC/GC to just a DC (e.g., uncheck the GC checkbox and reboot). You will still need to change the LDAP port used by Exchange 5.5 from TCP port 389 to something else (e.g., port 391).
Then, once you have everyone over on Exchange 2000, you can then make the existing DC a GC again.
This was first published in May 2002