just 笔记s for network（持续loading）

promiscuous mode：

   promiscuous mode (often shortened to "promisc mode" or "promisc. mode") is a mode for a wired network interface controller (NIC) orwireless network interface controller (WNIC) that causes the controller to pass all traffic it receives to the central processing unit (CPU) rather than passing only the frames that the controller is intended to receive

引用：https://en.wikipedia.org/wiki/Promiscuous_mode

   主机网卡一般默认不启动该模式，使用ovs建立网桥，桥接网卡使主机成为一个交换机，必须开启网卡的promisc mode（ubuntu14.04 下命令为 ifconfig eth0 promisc），不然交换机不会处理目的mac不是自己的接收网卡的数据包，也就无法进行转发了。