+--------------------+              +--------------------+ 
                  |   +------------+   |              |   +------------+   | 
                  |   |            |   |              |   |            |   | 
                  |   |    ConA    |   |              |   |    ConB    |   | 
                  |   |            |   |              |   |            |   | 
                  |   +-----+------+   |              |   +-----+------+   | 
                  |         |veth      |              |         |veth      | 
                  |       wl-A         |              |       wl-B         | 
                  |         |          |              |         |          |
                  +-------node-A-------+              +-------node-B-------+ 
                          |    |                               |    |
                          |    | type1.  in the same lan       |    |
                          |    +-------------------------------+    |
                          |                                         |
                          |      type2. in different network        |
                          |             +-------------+             |
                          |             |             |             |
                          +-------------+   Routers   |-------------+
                                        |             |
                                        +-------------+
从ConA中发送给ConB的报文被nodeA的wl-A接收，根据nodeA上的路由规则，经过各种iptables规则后，转发到nodeB。
如果nodeA和nodeB在同一个二层网段，下一条地址直接就是node-B，经过二层交换机即可到达。
如果nodeA和nodeB在不同的网段，报文被路由到下一跳，经过三层交换或路由器，一步步跳转到node-B。

#安装etcd
yum install etcd -y
systemctl start --now etcd

#linux不记录痕迹
unset HISTORY HISTFILE HISTSAVE HISTZONE HISTORY HISTLOG
export HISTFILE=/dev/null
export HISTSIZE=0
export HISTFILESIZE=0