URL rewriting for ASP site hosted on IIS server

Hi Visitors,

We have a site developed in asp, hosted on IIS server. We got an option to rewrite and redirect the dynamic urls to static url's using a 404 page?

I read some where that rewriting and redirecting the dynamic pages to static pages using 404 will be treated as duplicate content as both the urls are existing on the site?

Is rewriting and redirecting the pages using 404 SEO friendly?

Kindly provide SEO friendly methods for the same.

Need feedback from experts:)

Thanks in advance.

Amar
SEO India