It is true to say that there are no shortage of Search Engine Optimization experts or web hosting companies out there who are seemingly hell bent on telling their customers that they most definitely need to get separate IP addresses for each and every single one of their websites or suffer the wrath of Google who might punish them with ranking penalties or, even worse, by banning them from the SERPs altogether!
However, this is seldom the case and such penalties are only ever administered in the very rarest circumstances.
If you have two websites on the same C-block and they are both trying to promote themselves for the same set of keywords and search terms then this is perfectly acceptable and has been stated so by Google themselves on many occasions.
For example, if your website is hosted on a content delivery network then you will obviously ending up sharing an IP block with several other companies, many of which may be within the same industry or service sector as your company. Shared hosting sites also present similar circumstances – so if you are in this situation then the truth of the matter is that you have very little to worry about in terms of page rank and your SEO positioning for your keywords in the natural search results.
So, the moral of the story is that you don’t have to buy an artificial IP addresses in order to move things around as far as Google is concerned. Provided your content is fresh, relevant and well-written, then there is no need to rewrite everything from scratch for the sake of it in order to avoid being penalized by the search engines.
The whole purpose of a CDN is to provide a fast and effective delivery system depending on the geographical location of the end user, so providing unique content for every single user in every province would prove to be very expensive and simply impractical on every level. So, if you do rely on a Content Delivery Network, there is no need to worry about duplicate content being delivered by the same site using different IP addresses as Google make every allowance for this practice.