[JdeBP]

You are employing a faulty concept of what constitutes built-in. This is not Windows, or one of the BSDs. You're using one of the Linux distributions where everything is made up of installing packages. There is no meaningful "built-in"/"not-built-in" difference between installing one of these DNS server packages from a CentOS 7 repository and installing any other CentOS packages from a CentOS 7 repository.

> All software on a Red Hat Enterprise Linux system is divided into RPM packages which can be installed, upgraded, or removed.

-- https://www.centos.org/docs/5/html/Deployment_Guide-en-US/pt...

A (very) quick check indicates that the CentOS 7 "main" and "updates" repositories have at least three of the DNS softwares that I mentioned. Ubuntu 16 is better endowed, and has all of them that I mentioned, and an additional "Debian fork of djbdns" that I did not, in Ubuntu's "main" and "universe" repositories.