網絡的混雜模式

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

   主機網卡一般默認不啓動該模式，使用ovs建立網橋，橋接網卡使主機成爲一個交換機，必須開啓網卡的promisc mode（ubuntu14.04 下命令爲 ifconfig eth0 promisc），不然交換機不會處理目的mac不是自己的接收網卡的數據包，也就無法進行轉發了。