Learning Windows Server 2003

Zones Versus Domains

As you learned in the previous section, a DNS domain in its simplest form is a second-level name coupled with an ICANN-sponsored top-level domain—hasselltech.net, for example. In DNS parlance, a zone is the range of machines and addresses that a specific nameserver needs to be concerned about. Zones don’t necessarily need to correspond to DNS domains, meaning that I can have multiple DNS zones for the single hasselltech.net domain. For example, I can have one zone for sales.hasselltech.net, another zone for billing.hasselltech.net, and yet another for hosting.hasselltech.net, all with separate nameservers but all within the control of the hasselltech.net domain.

Why would you want multiple DNS zones for a single DNS domain? To delegate administration is a common reason. If your organization is spread all over the country and you have an administrator for each office around the country, that administrator is likely best equipped and skilled to handle DNS configuration for his office—after all, he works with the individual computers more than a higher-level administrator at the home office does. So, the home office nameserver is configured to hold a few names and addresses for servers and machines there, and the branch office nameservers hold zones for their respective computers. In this configuration, when a computer comes to their servers and requests a name for an IP address associated with a branch office, the nameservers at the home office will refer ...