SOA records

The SOA (StartofAuthority) resource record is the start authority record, which is the most important and most commonly used resource record. Zones are based on the concept of a server authority. When a DNS server is configured to load a zone, it uses both SOA and NS resource records to determine the authority attributes of the zone.

SOA and NS resource records have a special role in zone configuration, they are records required for any zone and are generally the first resource records listed in the file.

The starting authority SOA resource record is always first in any standard zone, and it represents the DNS server that originally created it or is now the master server for this interception. It is also used to store other properties that affect zone updates or expiry, such as version information and timing, which affect how often data is synced between nameservers in this zone

In bind:
$TTL 3600
$ORIGIN texiangbao. com.cn.
@ IN SOA dns.qqdns.com. domainadmin.dnspod.com.(
1247134024 ;Serial
3600 ; Refresh ( seconds )
1800 ; Retry ( seconds )
1209600 ; Expire ( seconds )
3600 );Minimum TTL for Zone ( seconds )
;
@ IN NS dns.qqdns.com.
@ IN NS dns.ggdns.com.
www 3600 IN A 63.220.7.134
www 3600 IN A 63.220.7.134
;
;generated @ 2009-07-09 18:07:12
;end

Primary Server (Owner) The hostname of the primary DNS server for the zone.

The email address of the owner of the owner management area. Use a period (.) instead of the "at" sign (@) in the email name.

Serial Number The revision number of this zone file. This number is incremented each time the resource records in the zone change. It is important to increase this value every time a zone changes, so that partially or completely modified zones can be replicated to other secondary servers in subsequent transfers.

Refresh Interval The time, in seconds, that the secondary DNS server waits before querying the origin of the zone for zone updates. When the refresh interval expires, the secondary DNS server requests a copy of the zone's current SOA record from the origin server that responded to the request. The secondary DNS server then compares the sequence number of the origin server's current SOA record (as shown in the response) with the sequence number of its local SOA record. If the two are different, the secondary DNS server requests the zone transfer from the primary DNS server. The default time for this field is 900 seconds (15 minutes).

Retry Interval The time, in seconds, that the secondary server waits before retrying a failed zone transfer. Typically, this time is shorter than the refresh interval. The default value is 600 seconds (10 minutes).

The expiration interval is the time, in seconds, before the secondary server stops responding to queries after the elapsed refresh interval with no refreshes or updates for the zone. Because it expires at this time, the secondary server must treat its local data as unreliable. The default value is 86,400 seconds (24 hours).

Minimum (default) TTL The default time-to-live (TTL) for the zone and the maximum interval between cached negative-answer name queries. The default value is 3,600 seconds (1 hour).