Also called a zone of authority, a subset of the Domain Name System (DNS) namespace that is managed by a name server. This administrative unit can consist of a single domain, or it can be a domain combined with a number of subdomains. The concepts of a zone and a DNS domain are related: each zone is anchored in a specific domain known as the zone’s root domain.
The name server must have a zone file, which contains the mappings between IP addresses and host names for the zone. A name server can manage one or more zones, depending on how it is configured. For example, a name server might have one zone for the domain microsoft.com and another zone for the domain adventure.expedia.com. Depending on how the zone file is configured, a name server might be responsible for
Typically, at least two name servers are responsible for a given zone - a primary name server, which manages the actual zone file, and one or more secondary name servers for redundancy. The primary name server manages a standard primary zone, which is represented by a text file called a zone file. (You can modify this file by using a text editor such as Notepad or by using the Microsoft Windows NT administrative tool called DNS Manager.) Each secondary name server manages a standard secondary zone, which is represented by a read-only zone file that you obtain by copying the primary zone file from the primary name server via a process called zone transfer.
Graphic Z-1. Zones and domains in DNS.
In Microsoft Windows 2000–based networks, a zone can take yet a third form, called an Active Directory integrated zone. In this type of zone, the zone information is stored and integrated into Active Directory of Windows 2000 for security purposes and is replicated by using the standard directory replication method used by Windows 2000 domain controllers. DNS in Windows 2000 supports dynamic update to ease the administrative burden of manually maintaining zone files.