CNAME flattening is a service that allows you to have a CNAME at the Apex of your DNS Zone without breaking the DNS Specifications.
This article describes how to configure the service on any DNS zone hosted by DDNS.
It is not possible to add a CNAME at the Apex of your domain name so we have created a custom record which will allow you to specify a CNAME Alias for our servers to follow and resolve this to an IP Address. The IP address will be updated automatically if there is any change in the CNAME the service is following.
How to activate it
Open the DNS Settings in the hosting control panel, click on Add Record.
Set Type as TXT and enter _cf in the domain name field.
In the TXT Record field enter the CNAME target you want the apex domain to follow e.g. "cloud.example.com" without the quote marks.
Click OK to save and then click update to push your change.
Wait 10 seconds and reload the DNS zone page. The user should now see that the A record for the domain has been updated with the IP address of the resolved CNAME target. An additional TXT record named "_cfwarn" will now be visible, warning the user of the CNAME flattening feature being enabled on the domain and referring them to this article.
Deactivate CNAME Flattening
To deactivate the service simply remove the _cf and _cfwarn TXT records from DNS Settings in the Plesk control panel. The system will stop polling the record within 5 minutes.
- CNAME flattening only applies to the apex aka "naked" domain. It can't be used to flatten other records in the zone.
- If there are multiple Address (A) records for the apex domain these must be removed for the service to work, only a single Address record is supported.
- Domain aliases are supported, if you have DNS enabled and DNS syncing switched on the Alias will automatically be flattened in the same way as the parent domain.
- You can't have more than one _cf record in a zone.
- The Serial format on the SOA record for the zone will be set to timestamp and the ttl, refresh, retry and minimum values will also be updated to support a 5 minute refresh rate. See the SOA tab in the Plesk DNS zone page for the updated domain. These settings won't be changed after removing the _cf records.
- When the DNS Service is cancelled this service is automatically removed.