https://www.youtube.com/watch?v=_z6do5BSJmg
https://www.youtube.com/watch?v=o66UFsodUYo
역방향 DNS ISP에 신청해서 하는 거 등록하는 법
https://midasitwebop.tistory.com/m/99
https://velog.io/@dlwoguq0928/%EC%8B%9C%EB%86%80%EB%A1%9C%EC%A7%80-%EB%A9%94%EC%9D%BC-%EC%84%9C%EB%B2%84-rDNS-%EB%93%B1%EB%A1%9D-%EC%8B%A0%EC%B2%AD-KT
DNS Record 종류
https://foxydog.tistory.com/28
