https://blog.wongcw.com/2018/10/16/natcloud%ef%bc%9a5%e5%85%83-%e6%9c%88-128mb%e5%86%85%e5%ad%98-4gb-ssd%e7%a9%ba%e9%97%b4-700gb%e6%b5%81%e9%87%8f-nat-kvm-%e6%b3%a2%e7%89%b9%e5%85%b0/