Hi, you no need any DNS entries for the building this cluster example, set the hostname you need and ther you can add it to the /etc/hosts on all nodes, like this for example for mine 1 master node:

root@kube-master1:~# cat /etc/hosts
127.0.0.1 localhost
xx.xx.xx.xx kube-master1

Do the same for all your nodes, kubeadm will take this hostnames when will crerate the cluster.