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HI Chris We have been using CDN networds to achieve this for many years and have not seen any issues with duplicate content. As I understand it, one piece of content should only exists at one URL. So if the same URL is served from a number of different IPs there should be no issues with duplicate content. To make absolutely sure you can keep an eye on warnings in Google Webmaster tools and implement canonical tags. Hope this helped to shed some light on this issue. Have a great day Fredrik