PTR (pointer) records are the reverse of A records: whereas the latter maps names to addresses, PTR addresses map addresses to names. PTR records are not stored in the main zone database for mydomain.com, but in another database which covers reverse lookups. There is a special domain set aside for reverse lookups: in-addr.arpa
. PTR records reference addresses with respect to this zone. In practice, this means that when creating a PTR record, the numerical address is reversed and followed by "in-addr.arpa." So the PTR record for the IP address 192.168.40.34
would refer to it as 34.40.168.192.in-addr.arpa
.
Below is the example of the reverse zone:
40.168.192.in-addr.arpa. IN SOA ns1.mydomain.com. root.mydomain.com. (
2004031101 ; Serial
10800 ; Refresh
3600 ; Retry
3600000 ; Expire
86400 ) ; Minimum
;
34 IN PTR first.mydomain.com.
The reverse DNS zone appears as soon as the A record is added to the direct zone. The single reverse zone is created for IP addresses from the single subnet. For example, if you add an A record that maps the domain third.mydomain.com
to the 192.168.40.55 address, the corresponding PTR record will be added to the reverse zone described in our example:
55 IN PTR third.mydomain.com
To edit a reverse DNS zone:
Note: Using the Parallels Business Automation - Standard web-based interface, you can manage only the reverse zones created for IP addresses that stored in the Parallels Business Automation - Standard database. For external IP addresses reverse zones are not created.
Note: The minimal default TTL for all the resource records containing in the zone file is indicated in the Domain Manager > Setup > General. And this default TTL can be re-defined for every record containing in the zone file. Thus, if you leave the TTL field empty, then the default minimal TTL will be applied to this record.