Creating an A record and then a CNAME to point a subdomain to a different server gives an error message

Question

I am trying to point a subdomain to a different server. The A Record changed without issue but the CNAME won't save in cPanel.

I get this error:

Error: sub.domain.com. already has a A record. You may not mix CNAME records with other records for the same name.

How do I fix this?

Answer 1

A and CNAME both are types of DNS records, that can be applied to a domain name.

But they are mutually exclusive:^[1]

• A resolves a domain name query to an IP address,
• CNAME resolves it to an other domain name.

So if you are ”trying to point a subdomain to a different server“ it depends on you hosting situation if it's better to have DNS queries resolved directly to the new server's IP by setting the subdomain's A record to the new IP or "redirect" the DNS lookup by setting CNAME to point to a domain name of the new server (which gets DNS-resolved iteratively).^[2]

(I certainly have no crystal ball, but person asking the question may confuse a CNAME record to be some kind of alias naming mechanism.)

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1. Actually, a domain name having a CNAME attached must not have any other resource record associated.
2. NB: In the case of HTTP requests to the mentioned subdomain, the host: header will not change during a CNAME resolution.

Answer 2

The error message strongly indicates that you already have an A record for the subdomain.

You need to delete this A record before adding the CNAME record as the 2 record types are incompatible with each other.

Answer 3

To fix this, you will have to login to your Cpanel, then go to Zone Editor (DNS). From there, select the "domain" you are trying to update. Then from the list, there's should option where you can view all "A records" - just delete the "A records" of the sub-domain you have added.