It is not, in fact. At least it should not be. Because “custom name servers” as appears in the Cloudflare’s respective page: “Custom nameservers allow you to create your own, unique nameservers in place of your assigned Cloudflare nameservers”. That is to say “create YOUR OWN UNIQUIE name servers”. No, this is not managing the DNS outside Cloudflare. This is as it says, “creating” custome name servers; custom for the domain. But I don’t want to create a name server, I want to use an “existing” name server.
To exemplify it simply;
Let’s say my domain is example[dot]com
Per the explanation of Cloudflare, “creating custom name servers” mean to create name servers like:
ns1.example.com
ns2.example.com
But what I want to do is, use an existing name server like:
ns1.some-dns-provider.com
ns1.some-backup.com
If it is also done in the same menu, then the explanation and terminology of Cloudflare is extremely misleading.