What is the difference between Reverse DNS and PTR Record?

harrygreen90

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Sometimes I get confused between using Reverse DNS and PTR Record? can any one tell me what is the difference between Reverse DNS and PTR Record?

where to set them and a real example if possible. Thanks
 

edisonvpb

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These are different ways where you point your ip to domain
 
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vishwa

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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.
 

HM-Mike

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Collabora

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Reverse DNS (rDNS) turns an IP address into a hostname -- for example, it might turn 1.2.3.4 into host.mydomain.com. The PTR record is a DNS server record entry that allows rDNS. The PTR record is the answer to a Reverse DNS (rDNS) query. In the familiar forward DNS query, the A record is the answer.

Some will tell you:

Forward: hostname is mapped to your IP address, e.g., host.mydomain.com ---> 1.2.3.4
Reverse: IP address is mapped to your hostname, e.g., 1.2.3.1 --> host.mydomain.com

However, this is not usually the case -- especially in the web hosting world. In reality, forward DNS for "host.mydomain.com" pointing to IP address "1.2.3.4", does not necessarily mean that rDNS for IP "1.2.3.4" also points to "host.mydomain.com." A special PTR-record type is used to store reverse DNS entries. The name of the PTR-record is the IP address with the segments reversed + ".in-addr.arpa". For example the reverse DNS entry for IP 1.2.3.4 would be stored as a PTR-record for "4.3.2.1.in-addr.arpa".

To make things more confusing, the PTR record is not stored on the same DNS server as the A record. For example, you will see the A record for your domain in cPanel DNS. However, you would not put a PTR record there. The PTR will be entered on the IP address owner's DNS server. This may not even be your web host -- its usually the upstream provider or ISP that owns the IP address. If you need to set up a PTR record for your domain you will need to submit a ticket to your host.

In the web hosting world, there is only one reason to have a PTR record. Many e-mail servers on the Internet are configured to reject incoming e-mails from any IP address which does not have reverse DNS. So if you send mail to another mail server a reverse DNS must exist for the IP address that your outgoing e-mail is sent from. It does not matter what the reverse DNS record for your IP address points to as long as it is there (e-mail servers checking for reverse DNS do recognize that it is normal to host many domains on a single IP address and it would be impossible to list all those domains in reverse DNS for the IP).
 

Jackleo7878

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I'd love to explain in a simple way PTR is short of a pointer, it is straightforward, by checking the IP address, you get to the host name/domain.

For every A record, there should be a PTR record. It is different from how the DNS works, rather of writing the domain and taking to the A record, you start with the IP address and get the domain name.
 

Aby

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Reverse DNS:
Its main function is to translate the numeric addresses of the websites - the IP addresses, to domain/host names, as opposed to the Forward DNS process. The Reverse DNS refers also to locating which domain name/host belongs to a given IP address, which is why this process is often referred to as Reverse DNS lookup.

PTR Record:
The 'pointer' record is exactly the opposite of the 'A' record; the PTR address will give you the domain associated with a given IP address. The PTR record is used in reverse-lookup zones for reverse DNS searches.
 
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