As Explained by Steve, you will must prepare the parent domain for the schema updatation before you install Exchange 2010 in child domain. Setup.com/preparead command needs to be run on only Schema Master role which resides in parent domain. setup.com /preparead
command will update the root domains configuration partition by adding Exchange schema and many other Exchange releated containers. Once the replication from Parent domain to child domain is successful you will have to install all prerequists for Exchange
2010 on child domains exchange server and install exchange 2010.
Sudhir Bidye.
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