Reverse DNS

Reverse DNS maps an IP address to a hostname .

The reverse domain name service (rDNS) serves several different purposes from email to network troubleshooting. Some 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.
  • Evaluating which hostname is affected when maintenance is performed on an IP address.
Note

You can only create reverse DNS zones for IP ranges that you control. Contact support to request a reverse DNS (PTR) record for an IP address owned by Oracle. For example, a public IP address that was automatically assigned to a Compute instance or Load Balancer. For more information, see Reverse DNS (PTR).

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

After you create and publish a reverse DNS zone and PTR records, you can update the reverse DNS zone delegation with the IP provider. Delegation changes aren't required with the 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 a IP address block type.

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

Setting Up Reverse DNS for Full Address Block