I have searched but don't know what I am looking for. :) And here I found so similar.
My site is monpage.com. I would like to use tumblr as a blog service for my site. The URL would be monpage.tumblr.com. At tumblr, there offers a domain mapping service. So:
Yesterday, I set up a http://blog.monpage.com to point to a newly setup http://monpage.tumblr.com. Following instructions, all I did was that I have to have the A-record for blog.monpage.com pointing to their IP.
My question is how do they do that? The clever thing is keeping blog.monpage.com in the address box like a part of your site. With mod_rewrite? I would like to provide the same service to my clients. Thanks!