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Reverse IP Lookup – DNS Checker

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Reverse DNS lookup

tool

The Reverse DNS Check tool queries the specified IP to resolve it to a host name. The hostname is something like a normal domain or subdomain, i.e. google-public-DNS-a.google.com. This hostname is Google’s hostname against IP 8.8.8.8, which is Google’s public DNS IP. If you enter your IP, you can point to your ISP’s hostname, or if you check your server’s IP, it can show you your domain name on which it resolves.

What is the DNS PTR (pointer) record?

A PTR record, known as a pointer record or reverse DNS record, is the type of Domain Name System (DNS) record used to store the domain or host name of an IP address. Maps an IP address to a host name.

PTR records, called “reverse DNS” records, are used in reverse IP lookup. You can get the associated domain name or host name using the IP address.

PTR record lookups are the opposite of an A record lookup for an IPv4 address and an AAAA record lookup for an IPv6 address.

Typically, a user

wants to establish a connection to a server with an already known domain name, but the user does not have the correct IP address. When a user enters a domain name into the browser, the DNS lookup process occurs, matching the domain name to an IP address.

A reverse DNS lookup or reverse IP address lookup

is an opposite process that starts with an IP address and ends with the associated domain name or hostname lookup. Here the user already knows the IP address and wants to find the domain or hostname associated with that IP.

How are DNS PTR records stored?

The structure of the PTR record is the same as other types of DNS records. The different pieces of information are arranged in the register in their relevant fields.

<name> <ttl> <class> <type> <rdata>

Here

<name>:

  • It is populated with the IP address. <
  • ttl>: It’s time to live. It is the time in seconds for which the input is valid. When it expires, it must be activated again.
  • <class>: Contains the abbreviation of the DNS record class being used.
  • <type>: Has the record type. that is, PTR.
  • <rdata>: Contains the data of the resource, domain or host name.

The syntax is similar to that of a record, but the contents of the field differ. Here, one thing is essential to remember is reverse mapping. Therefore, the IP address is specified in reverse sequence.

In IPv4

An, a record must exist for each PTR record. A PTR record stored as the IP address is divided into segments and then reversed, followed by .in-addr.arpa. (is the namespace within .arpa for IPv4 reverse DNS lookups.)

For example, the PTR record of the IPv4 address 8.8.4.4 for the domain dns.google will be stored in 4.4.8.8.in-addr.arpa.

In the preceding example

  • , 4.8.8.in-addr.arpa. represents the identifier for the record. This is the PTR record for An 8.8.4.4
  • record PTR is the DNS record type

    • .

  • Google is the registry value. This is the domain or host name associated with the IP address.
  • 3600 is the TTL (Time to Live).

In

IPv6, IPv6 addresses

are composed differently than IPv4 addresses, and IPv6 PTR records exist in their distinct namespace within .arpa. PTR records for IPv6 are stored under the IPv6 address, reversed, and converted to four-bit sections (as opposed to 8-bit sections, as in IPv4), plus .ip6.arpa.

For example, the PTR record for IPv6 address 2001:4860:4860::8844 for the domain dns.google will be stored at 4.4.8.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.00.0.0.0.0.0.0.0.0.00.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.00.0.0.0.0.0.0.0.0.0.0.00.0.

.

In the example above

, 4.8.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.6.8.4.0.6.8.4.4.1.0.0.2.ip6.arpa.

  • Represents the ID of the record. This is the PTR record for A record 2001:4860:4860::8844
  • PTR is the DNS record type

    • .

  • Google is the registry value. This is the domain or host name associated with the IP address.
  • 3600 is the TTL (Time to Live).

How to check PTR record or perform reverse IP lookup?

1. On Windows, Linux, or macOS

If you’re using Windows, run nslookup IP_address at the command prompt. If you are using Linux or MAC OS, run dig -x IP_address in the Linux console terminal or MacOS terminal.

Note: Replace the IP_address with the IP address of your domain.

2. Using IP Reverse LookupTool

Just enter the IP address and click the “Submit” button. The reverse IP address lookup will perform the reverse IP lookup and provide you with the result.

Also, check PTR records across multiple DNS servers around the world with the WhatsMyDNS tool.

What are the primary uses of PTR records?

PTR records are used in reverse IP address lookups. These logs are essential for outgoing mail servers.

Some email servers such as Gmail and Yahoo mail use spam filters to check whether the IP address of a server trying to deliver mail has matching forward and reverse DNS records. It helps to verify the domain or hostname of an email address and see if the legitimate email server is likely to use the associated IP addresses.

As anti-spam filters perform these checks, email delivery issues may occur due to a misconfigured or missing PTR record. To send the PTR record by mail is mandatory. Email services can block or reject all emails from that domain if a domain does not have a PTR record or if the PTR record contains the wrong domain or host name. Mail servers use them to ensure that emails come from the location they claim to come from.

Frequently Asked Questions

Do I need PTR records?

The simple answer is yes. Email is integral to the business, and the use of PTR records is in Google’s best practices.

You never want your email to bounce or be part of a spam folder. It damages your trustworthiness and credibility and makes your customers wonder why their email doesn’t make it to their inboxes.

Can I have multiple PTR records?

Typically, a PTR record can point to a single hostname through the IP reverse lookup process. But what if you need multiple PTR records for a single IP to point to multiple hostnames? That will work when you have multiple domains registered; they all have the same IP address as the DNS A record.

The Domain Name System does not restrict the number of entries, but it is not recommended to have multiple PTR records at all. Because the software running mail servers often expects only one entry for each

IP address, “One IP – One PTR.”

A server can randomly choose one during a reverse lookup IP if

multiple PTR records are defined for a single IP address.

There is no feature available to prioritize

PTR records, such as MX records.

Also, adding multiple PTR records for a single IP address does not improve reliability. And it can even result in failed verification of A/PTR records and reduce the email delivery ratio.

How long does it take for a PTR record to propagate?

It usually depends on how often the hosting company updates zone files. Even if you update the PTR records from the hosting panel control panel, the hosting company immediately updates your zone files after those updates. Still, it takes time because of DNS TTL. Typically, it takes 24 to 48 hours for DNS records to propagate globally. You can use my DNS checker to check whether or not your PTR records propagate across all DNS servers globally.

Looking for more DNS tools in DNS Checker? Why not try our CNAME Checker, Name Server Checker, and MX Record Checker? All DNS tools are top-notch and free!

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