Domain forwarding is kind of interesting. There must be 200 settings you have to change by hand to make sure people trying to get to your site get to the place they want to get to. You have www.url.com, ftp.url.com, billyjoebob.URL.com all to worry about. These first set of characters before the first dot are called subdomains. The owner of the domain has control over them for the most part.
My blog here is plastickelly.blogspot.com. Blogspot has some script set up that when someone signs up for a blog at that URL, creates the DNS entry that points people to their blog. When someone enters www.blogspot.com they go the blogspot's front page, which I believe still pints to Blogger's front page. This is all done with domain forwarding which is done with DNS entries.
This morning I got an email that said "We got domain3. Please forward it to domain1." No problem chief.
I forward domain3 to domain1. Sounds easy. Well, I forwarded domain3.com to domain1.com. I looked at domain2.com and it was forwarded to www.domain1.com. I had to go back and change the forward for domain3 to say www.domain1.com.
It can take 48 hours for the changes to take effect. DNS is a funny beast. All the servers all over the world just talk to one another and eventually your settings make it all over the planet. There is as much voodoo as programming involved.
Will my changes make it round the planet in 48 hours of 96? I had to make the two changes one right after the other. Will the second change simply supplant the first? I doubt it. More likely One change will chase the other round the planet from server to server. With all the confusion of time stamps, I fear half the servers in the world will have one setting and half will wind up with the other. They will probably both work.
It took about an hour for the changes to take affect. No world wide game of cat and mouse. All quite boring.