No, same domain but the URL's will differ on the new site. So,

the old site may have had this URL:
http://www.websitename.com/Content.asp?P=1

and the new site may have the rewritten version at
http://www.websitename.com/AboutUs.aspx

..which is easy enough to redirect obviously. It's the pages that don't have new versions I'm concerned about. I guess they could happily sit there still but not sure if that's the right way to go....