Dns Zones

The DNS stands for the Domain Name System and a DNS zone is a segment of the global DNS namespace for which the responsibility of administration has been delegated. DNS data is divided into convenient sets of data called zones. Zones consist of a name and IP address information about one or more parts of a DNS domain. A server which contains all of the information for a single zone is the commanding server for the domain. Sometimes the authority for answering DNS queries for a particular sub domain is handed over to another DNS server. In this situation, the DNS server for the domain can be configured to refer to the sub domain queries to the suitable server.

Zone data is sometimes stored on servers other than the authoritative DNS server for backup purposes. The servers which load data from the authoritative server are known as the secondary servers. Configuring secondary servers provides a backup and redundancy in case the primary server goes down and allows you to balance the demand on servers. Secondary servers acquire zone data by doing zone transfers from the commanding server. When a secondary server is launched it starts loading a complete copy of the zone data from the primary server. The secondary server also tends to reload zone data from the primary server or from other secondary servers for that domain in case zone data changes.

There are two types of zones:

1.    Primary zone:

Primary zone Loads zone data directly from a file on the host. A primary zone may consist of a subzone, or a child zone. It also includes resource records such as host, alias, address, or reverse mapping pointer records.

2.    Secondary zone:

Secondary zone loads zone data from a zone's authoritative server or any other secondary server. A secondary server maintains a complete copy of the zone for backup.