Q:

What exactly goes in creating a subdomain

I recently got myself a domain name. I wanted to add a couple of sub-domains to it.
I want to know what goes on when you create a new sub-domain. How does a router know how to resolve a sub-domain.
Some hosting providers also charge for creating them. Do they incur legitimate expenses to create and manage these or is it pure profit?

A:

If your domain host charges for sub domains, find a new host, that kind of service should be free. If you are not sure where to find one, check out zonedit.com . Their domains update in almost real-time, and they give you plenty of control. They also have guides for how to add sub domains. When you make a subdomain it will point to an IP address, this can be any public IP address, including ones that you used on other sub domains.
As for the costs to a business to add a subdomain. The cost is so small it is legally immeasurable. It is adding a few lines of text to a config file in a server somewhere. Charging for this server is a rip off, instead of charging for domain hosting as a whole.

