Welcome to the Q&A Forum

Thank you for both responses... Nakul-- I have been following everything exactly as you have described. In general the goal during the development was to keep changes to an absolute minimum. This has not always been possible. The majority of external links have been 301 redirected or in cases where the new server responds to two differnet URLs for the same content a canonical tag has been added. I have noticed that 99% of the reported URLs are former internal links.  The reported 404s are completely out of proportion (194k vs less than 5k pages in the new xml sitemap). I am really worried. Is there anything else I can do beside monitoring and hopping? How long does it  typically take to for "Things have to work their way out of its system."? Is it possible that Google is somehow accessing the old IP address (although the DNS records for the domain have changed)? We left the old server alive and planning to shut it down after the second site has been moved away from it. Thanks, Adam

If both cases display the same exact content via different URLs, then you don't want to return 200 status codes for both versions. A 301 redirect might work but since they are for the same exact page, it's possible you might run into an infinite redirect loop and make your pages completely inaccessible. As a result, I would recommend using the rel="canonical" tag to designate which URL is the correct one for the search engines to index.