A. If you want to force the Exchange server to use a specific GC instead of letting the server automatically choose a GC, you can perform the following steps:

  1. Start the Microsoft Management Console (MMC) Exchange System Management (ESM) snap-in (Start, Programs, Microsoft Exchange, System Manager).
  2. In the treeview pane, navigate to Administrative Groups, &ltadministrative group name&gt, Servers.
  3. Right-click the server and select Properties.
  4. Select the Directory Access tab.
  5. From the Show drop-down list, select Global Catalog Servers.
  6. Clear the "Automatically discover servers" check box.
  7. Click Yes in the confirmation box.
  8. Click Add.
  9. Enter the name of the GC to use.
  10. Click OK.

Microsoft recommends that you don't manually set the GC that Exchange Server uses; therefore, you should manually set the GC only when it's absolutely necessary.