March 2021
$ORIGIN org.
$TTL 5m
;
example IN SOA ns1.example.org. hostmaster.example.org. (
20210326 ; serial
4h ; refresh - wait between refresh attempts by secondary
15h ; retry - retry failed zone refresh by secondary
8h ; expire - expiration of secondary authority
4m ; negative result TTL
)
;
IN NS ns1.example.org.
IN NS ns2.example.org.
MX 10 mail1.example.org.
MX 20 mail2.example.org.
;
IN TXT "v=spf1 a mx a:mail1.example.org a:mail2.example.org -all"
IN NAPTR 10 100 "s" "SIP+D2U" "" _sip._udp.example.org.
_sip._udp IN SRV 10 100 5060 p1.example.org.
_sip._udp IN SRV 20 100 5060 p2.example.org.
;
ns1 IN A 203.0.113.110
ns2 IN A 198.51.100.33
mail1 IN A 192.0.2.36
mail1 IN AAAA 2001:DB8::6
mail2 IN A 203.0.113.42
www IN CNAME example.org.
p1 IN A 203.0.113.27
p2 IN A 198.51.100.154
A fully-terminated hostname has a dot on the end, like foo.example.com..
The $ORIGIN org. directive tells bind to append org. to any hostnames that appear after the directive that are not fully terminated.
An $ORIGIN directive can be used more than once in a Bind config file, and affects all hostnames that appear after it (until the next $ORIGIN directive).
The $TTL 5m directive sets the default time to live for records in the zone.
This is the time after which clients should ask again for a potentially updated record.
Like $ORIGIN, the $TTL directive can be specified more than once in the same file.
The start of authority (SOA) record:
example IN SOA ns1.example.org. hostmaster.example.org. ( …
example is the hostname.
We could have written this as example.org., but the $ORIGIN directive will terminate the name with the TLD for us.
IN specifies the record type as “Internet”.
Other record types are rarely used.