Every other reference to this feature is linked to this post: http://www.howtoforge.com/forums/showthread.php?t=432
However, I'm looking to deploy a public preview and have been 50% successful. What has worked thus far:
I have domainB.com that is a on the server and works as is.
On my parent domain, domain.com, I setup a CNAME record that resolves domainb.domain.com to domainb.com - and it works.
But, where I run into conflict is where the domain is a legit domain not on my server (e.g. I'm developing a new site for a client, and their current live site is on another server; but i want to give them a preview and
have it all ready and setup under their tld).
I tried this demo by actually creating "microsoft.com" as a domain (which obviously I don't own) and then created the DNS entry CNAME subtest microsoft.com. (thus, subtest.domain.com resolves to microsoft.com). My thinking is that since there is a 'microsoft.com' available locally, that it wouldn't bother to go find the real one. That isn't the case in practice.
Any ideas of how I can improve this? Am i going about this the right way?