What is a Zone file?
A zone file is a text document used by the domain name system (DNS) to map computers, domain names, and various resources to the appropriate Internet Protocol (IP) addresses. This mapping allows people to access resources and computers on the Internet using human-readable addresses. Zone files generally consist of two parts: directives and resource records. Directives begin with a dollar sign, and include information that applies to the entire zone file, such as its time to live ($TTL). TTL is the default amount of time a name server should consider downloaded zone file information valid before checking for updates. For example, if the $TTL is set to 86,400 seconds (24 hours), a name server accessing that zone file will store a copy of it for 24 hours before attempting to look for an updated version. Note that individual resource records may include unique TTL information that overrides this default value. Other common directives include $ORIGIN, which sets the default domain name for
A zone is another name for a domain name or a sub-domain in a DNS server. Every domain and sub-domain has a zone. These zone files contain records, in plain text, which hold the DNS information that links a domain or sub-domain name to an IP address. Each zone file usually contains several different records. The difference between zones and domains is hierarchy. A domain can have a sub-domain contained within its hierarchal structure. While that sub-domain also has a zone, it’s not considered a sub-zone. There is no such thing as a sub-zone. All zones are a separate entity. While zones can be linked, they do not have a hierarchal structure.
