https://blog.offline-net.com/2010/10/03/dtiserversmanvpsip%e3%81%98%e3%82%83%e3%81%aa%e3%81%8f%e3%81%a6fqdn%e3%81%a7%e3%82%a2%e3%82%af%e3%82%bb%e3%82%b9%e3%81%97%e3%81%9f%e3%81%84/