What is the difference between Reverse DNS and PTR Record?

[harrygreen90]

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]

These are different ways where you point your ip to domain

 

[vishwa]

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]

HM-Mike

Spot on Vishwa!

 

[vps9]

PTR records are used for the reverse DNS lookup.Using the IP address can get the associated domain name.

 

[Collabora]

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]

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]

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.

 

[Server Trafficweb]

DNS can be tricky. There is a lot to know and, even when you think you have a firm grasp on it, surprises still pop up. Reverse DNS and PTR record configuration is one of those sneaky topics, but it's crucial to SPAM prevention during email delivery.

For some reason I was unable to find a clear and simple answer out there for how to accomplish this task, so that is my goal with this post. A simple explanation of reverse DNS is that it’s the exact opposite of DNS. Standard (aka forward) DNS maps a domain name to an IP address whereas reverse DNS maps an IP address to a domain name. The two are distinct and separate lookups however. Just because a forward lookup of example.com resolves to 1.2.3.4 doesn’t mean that a reverse lookup of 1.2.3.4 will resolve to example.com.