https://blog.wongcw.com/2018/12/30/h3c%e5%92%8ccisco%e4%ba%a4%e6%8d%a2%e6%9c%ba%e7%a6%81%e6%ad%a2mac%e5%9c%b0%e5%9d%80%e9%80%9a%e4%bf%a1/