https://rein.kr/posts/2010-09-19-ipv6-%EB%A5%BC-%EB%8C%80%EB%B9%84%ED%95%9C-%EC%BD%94%EB%93%9C%EB%A5%BC-%EC%A7%A4-%EB%95%8C-%EA%B0%80%EB%81%94-%EB%B3%B4%EB%8A%94-%EC%8B%A4%EC%88%98/