Oracle Cloud Infrastructure Documentation

Setting Up Reverse DNS Zones

Reverse DNS, or rDNS, maps an IP address to a hostname. Reverse DNS serves a number of different purposes from email to network troubleshooting. Some of the benefits include:

  • Adding a label for network troubleshooting tools such as traceroute.
  • Populating the “Received:” header field in an SMTP email.
  • Checking for generic reverse DNS such as 1-2-3-4.example.com to identify spammers.
  • Verifying a relationship between the owner of a domain name and the owner of the server (IP address).
  • Writing a human readable hostname to the log files for system monitoring tools.
  • Determining which hostname is affected when maintenance is performed on an IP address.

Before getting started with setting up reverse DNS within your Oracle Cloud Infrastructure account, contact your IP provider and confirm that they allow delegation of your reverse DNS zone. If they do not allow delegation, typically they can host your pointer record (PTR) for you and no reverse DNS configurations are required within your Oracle Cloud Infrastructure account. If they do allow delegation, confirm the exact syntax of the reverse DNS hostname with them, as some providers use slashes and some use dashes. Additionally, if you are delegating a reverse DNS zone, confirm that this zone matches exactly what you configure in your Oracle Cloud Infrastructure account as this is necessary in order for delegation to work properly.

After you create and publish your reverse DNS zone and PTR records, you can update your reverse DNS zone delegation with your IP provider. Delegation changes are not required with your domain registrar with a reverse DNS zone.

Setting up a reverse DNS zone is different for the two types of IP address blocks. Use the following procedures to set up a reverse DNS zone for your IP address block type.

Using the Console

Setting Up Reverse DNS for Classless Address Block (Partial Range of IP Addresses)

To find your reverse DNS zone name using classless address block
To create your DNS zone
To create a pointer record (PTR) for each host address
To add CNAME records for each host at your ISP
To update your zone delegation

Setting Up Reverse DNS for Full Address Block

To find your reverse DNS zone name using full address block
To create your DNS zone
To create a pointer record (PTR) for each host address
To update your zone delegation