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Since I don't know the exact nature of your duplicate pages, its a little hard to give a solid answer. Firstly, a canonical is a signal not a directive... so the search engines can choose to disregard it. Second, there are a few ways to consider handling duplicate page content. If your duplicate needs to exist for some reason and is a straight copy of another page or features a duplicate subset of content found on another page, then you could consider a canonical. If the duplicate page serves no real purpose and there is a better version of it elsewhere, then you could go with a 301. If the page needs to exist but could be re-written into something more relevant than its current state, do some tweaking to make it unique.