# Zone file | | A Domain Name System (DNS) **Zone file** is a text file that describes a DNS zone. A DNS zone is a subset, often a single domain, of the hierarchical domain name structure of the DNS. The zone file contains mappings between domain names and IP addresses and other resources, organized in the form of text representations of resource records (RR). A zone file may be either a DNS master file, authoritatively describing a zone, or it may be used to list the contents of a DNS cache. | |-|-| | | wikipedia:: [Zone file](https://en.wikipedia.org/wiki/Zone_file) | [[BIND]] uses the same format. [RFC 1035: Domain names - implementation and specification](https://www.rfc-editor.org/rfc/rfc1035#section-5.1) ## Example ``` $ORIGIN example.com. ; designates the start of this zone file in the namespace $TTL 3600 ; default expiration time (in seconds) of all RRs without their own TTL value example.com. IN SOA ns.example.com. username.example.com. ( 2020091025 7200 3600 1209600 3600 ) example.com. IN NS ns ; ns.example.com is a nameserver for example.com example.com. IN NS ns.somewhere.example. ; ns.somewhere.example is a backup nameserver for example.com example.com. IN MX 10 mail.example.com. ; mail.example.com is the mailserver for example.com @ IN MX 20 mail2.example.com. ; equivalent to above line, "@" represents zone origin @ IN MX 50 mail3 ; equivalent to above line, but using a relative host name example.com. IN A 192.0.2.1 ; IPv4 address for example.com IN AAAA 2001:db8:10::1 ; IPv6 address for example.com ns IN A 192.0.2.2 ; IPv4 address for ns.example.com IN AAAA 2001:db8:10::2 ; IPv6 address for ns.example.com www IN CNAME example.com. ; www.example.com is an alias for example.com wwwtest IN CNAME www ; wwwtest.example.com is another alias for www.example.com mail IN A 192.0.2.3 ; IPv4 address for mail.example.com mail2 IN A 192.0.2.4 ; IPv4 address for mail2.example.com mail3 IN A 192.0.2.5 ; IPv4 address for mail3.example.com ``` Periods indicate FQDN - [dns - FQDN format in Bind zone - Super User](https://superuser.com/questions/348282/fqdn-format-in-bind-zone#348284) > In the zone file, domain names that end with a full stop character (such as "example.com." in the above example) are fully qualified while those that do not end with a full stop are relative to the current origin (which is why www in the above example refers to www.example.com).