Sample Zone file
@ IN SOA NS.Opus1.COM. hostmaster.Opus1.COM. (
1998102601 ; serial number
43200 ; refresh 2x per day
7200 ; retry every 2 hour
2592000 ; expire after 1 month
IN MX 10 Cello.Opus1.COM.
IN MX 10 Viola.Opus1.COM.
IN MX 15 Tennis.Opus1.COM.
IN HINFO "DEC-VAXCLUSTER" "OPENVMS"
WWW CNAME Cello.Opus1.COM.
Tennis IN TXT "Game, set and match"
IN A 188.8.131.52 ; 100 Mbps line
IN HINFO "DEC-VAXSTATION" "OPENVMS"
IN MX 20 Mail.TheRiver.COM.
usually date, revision of last change
must be of increasing value for secondary to recognize the file has been modified
one of the most common problems in DNS is not properly updating this field for changes to propagate
Time in seconds for the secondary to contact the primary to compare serial number in SOA record
Time in seconds for the secondary to retry contacting primary if the primary did not respond at refresh minutes
How long the secondary should continue to answer queries for the zone if it loses contact with the primary
The time in seconds that a nameserver can cache a resource record for use in queries before needing to contact one of the authoritative nameservers