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I assume you have used some kind of rewrite on the server to change URLS to / rather than .aspx. This could be utilising some kind of redirect to move traffic from .aspx to /. Firstly, I'd check how the URLs are rewritten (if they are), Unfortuntaley my knowledge of windows server configs is limited, however in Linux I'd be checking my HT Access file and the redirect/rewrite rules. Once you have ascertained how the redirect us happening and solve the issue, then i'd implement the correct 301 redirects. I'd like to ask why you opted for name-of-page/ rather than name-of-page.aspx?