Cobra Forum

Question: Configure rDNS


Learn how to configure reverse DNS (rDNS) on Vultr instances using the Customer Portal or Vultr CLI.

Reverse DNS (rDNS) maps an IP address to a hostname using a PTR record, performing the opposite of a standard DNS lookup. Configuring rDNS allows services and monitoring tools to resolve your server's IP back to a fully qualified domain name (FQDN). Proper rDNS improves email deliverability, aids in network verification, and helps troubleshoot connectivity issues. Many services, including mail servers, rely on rDNS to verify legitimate sources, and monitoring tools use it to display human-readable hostnames.

Follow this guide to configure rDNS for Vultr instances using the Vultr Customer Portal or Vultr CLI.

Note
rDNS changes may take 6–12 hours to propagate and become active across the DNS system.

Vultr Customer Portal

1.Navigate to the Compute section under Products.

2.Select the instance for which you want to configure rDNS.

3.Click Settings, then choose IPv4 or IPv6 for which you want to set the rDNS.

4.Under Public Network, all your associated public IPs are listed. To update one, click the rDNS name under the Reverse DNS column.

5.Enter the FQDN you want to associate with your IP address.

6.Click the tick icon to save the rDNS record.

7.Run the below command to verify that the rDNS record is updated.

[color=blue]console[/color]


$ dig -x <instance-ip>
Code explanation

This command performs a reverse DNS lookup to find the domain name associated with a given IP address. The -x option tells dig to look up the hostname for the specified IP. Replace with the actual IP address you want to query.


The command above displays the PTR record associated with your IP.


Vultr CLI

1.Check the version of the Vultr CLI to ensure it is installed.

[color=blue]console[/color]


$ vultr-cli version

Output:

Vultr-CLI v3.7.0

2.List all available instances.

[color=blue]console[/color]


$ vultr-cli instance list

Note the id of the instance for which you want to update rDNS.

3.List all the IPv4 or IPv6 addresses associated with your instance.

• For IPv4 rDNS:

     1.List all associated IPv4 addresses for the instance.

[color=blue]console[/color]


$ vultr-cli instance ipv4 list <instance-id>

Note the IP address you want to configure rDNS for.

     2.Update the rDNS for the selected IPv4 address.

[color=blue]console[/color]


$ vultr-cli instance reverse-dns set-ipv4 <instance-id> <ipv4-address> --entry "<FQDN-rDNS>"

Output:

Reverse DNS IPv4 has been set

• For IPv6 rDNS:

     1.List all associated IPv6 addresses for the instance.

[color=blue]console[/color]

$ vultr-cli instance ipv6 list <instance-id>


     2.Update the rDNS for the selected IPv6 address.

[color=blue]console[/color]


$ vultr-cli instance reverse-dns set-ipv6 <instance-id> <ipv6-address> --entry "<FQDN-rDNS>"

Output:

Reverse DNS IPv6 has been set

4.Verify that the rDNS records have been updated.

[color=blue]console[/color]

$ dig -x <instance-ip>