How do I move a server to a different site?

Start the Microsoft Management Console (MMC) Active Directory Sites and Services snap-in. (From the Start menu, select Programs, Administrative Tools, Active Directory Sites and Services Manager.)

Expand the Sites container.

Expand the site that currently contains the server, and expand the Servers container.

Right-click the server, and select Move from the context menu, as the Screen shows.
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You’ll see a list of all the sites. Select the new target site, and click OK.