What is a PTR record and how to add/update mine?

You can think of the PTR record as an opposite of the A record. While the A record points a domain name to an IP address, the PTR record resolves the IP address to a domain/hostname.

PTR records are used for the reverse DNS (Domain Name System) lookup. Using the IP address you can get the associated domain/hostname. An A record should exist for every PTR record.

The usage of a reverse DNS setup for a mail server is a good solution. Some external mail exchange servers make reverse DNS lookups before accepting messages originating from your mail server.

You can check whether there is a PTR record set for a defined IP address. The syntax of the commands on a Linux OS are:

dig -x IP

or

host IP

For example, you can run the following commands in your Linux terminal:

dig -x 96.31.83.163

and the result would be:

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.30.rc1.el6_6.1 <<>> -x 96.31.83.163
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59024
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;163.83.31.96.in-addr.arpa.     IN      PTR

;; ANSWER SECTION:
163.83.31.96.in-addr.arpa. 15161 IN     PTR     enterprisevpssolutions.com.

;; Query time: 7 msec
;; SERVER: 8.8.8.8#53(8.8.8.8)
;; WHEN: Mon Jan  5 21:48:31 2015
;; MSG SIZE  rcvd: 83

or

 host 96.31.83.163

and the result would be:

163.83.31.96.in-addr.arpa domain name pointer enterprisevpssolutions.com.

The corresponding command under the Windows OS command prompt is:

nslookup IP

The reverse DNS lookup for IP version 4 uses a special domain – in-addr.arpa., while the lookup towards IPs version 6 uses ip6.arpa..

Detailed explanation of the reverse DNS lookup can be found in the following article:

http://en.wikipedia.org/wiki/Reverse_DNS_lookup

The rDNS service is provided for free and it can be requested by submitting a ticket to our support team from the client portal. There can be only one PTR record per IP address. Multiple PTR records can not be set for one IP.

kbadmin has written 146 articles

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