Understanding DNS
Domain Name System (DNS) is a distributed database system for managing host names and their associated Internet Protocol (IP) addresses. Using DNS means that people can use simple names, such as "www.jkltoys.com" to locate a host, rather than using the IP address (xxx.xxx.xxx.xxx). A single server may only be responsible for knowing the host names and IP addresses for a small subset of a zone, but DNS servers can work together to map all domain names to their IP addresses. DNS servers working together is what allows computers to communicate across the Internet.The different types of zones used in Windows Server 2003 DNS are listed below:
- Primary zone
- Secondary zone
- Active Directory-integrated zone
- Reverse lookup zone
- Stub zone
DNS data is divided into manageable sets of data called zones. Zones contain name and IP address information about one or more parts of a DNS domain. A server that contains all of the information for a zone is the authoritative server for the domain. Sometimes it may make sense to delegate the authority for answering DNS queries for a particular subdomain to another DNS server. In this case, the DNS server for the domain can be configured to refer the subdomain queries to the appropriate server.
For backup and redundancy, zone data is often stored on servers other than the authoritative DNS server. These other servers are called secondary servers, which load zone data from the authoritative server. Configuring secondary servers allows you to balance the demand on servers and also provides a backup in case the primary server goes down. Secondary servers obtain zone data by doing zone transfers from the authoritative server. When a secondary server is initialized, it loads a complete copy of the zone data from the primary server. The secondary server also reloads zone data from the primary server or from other secondaries for that domain when zone data changes.
DNS zone types
You can use iSeries(TM) DNS to define several types of zones to help you manage DNS data:
Primary zone
Loads zone data directly from a file on a host. A primary zone may contain a subzone, or child zone. It may also contain resource records such as host, alias (CNAME), address (A), or reverse mapping pointer (PTR) records.
Note: Primary zones are sometimes referred to as "master zones" in other BIND documentation.
Subzone
A subzone defines a zone within the primary zone. Subzones allow you to organize zone data into manageable pieces.Child zone
A child zone defines a subzone and delegates responsibility for the subzone data to one or more name servers. Alias (CNAME)
An alias defines an alternate name for a primary domain name.
Host
A host object maps A and PTR records to a host. Additional resource record may be associated with a host.
Secondary zone
Loads zone data from a zone's primary server or another secondary server. A secondary server maintains a complete copy of the zone for which it is a secondary.
Note: Secondary zones are sometimes referred to as "slave zones" in other BIND documentation. Stub zone
A stub zone is similar to a secondary zone, but it only transfers the name server (NS) records for that zone.
Forward zone
A forward zone directs all queries for that particular zone to other servers.
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