实现目标环境下的静态流表设置：
1 单个ovs上实现多个主机hosts之间的通信
2多ovs上多主机之间的通信

1 单个ovs上实现多个主机hosts之间的通信
使用函数定义的方式创建一个如下的拓扑，并使用静态流表

from mininet.net import Mininet
from mininet.node import OVSSwitch, Host
from mininet.cli import CLI
from mininet.link import Link
import networkx as nx
import matplotlib.pyplot as plt

def create_network():
    net = Mininet()
        # 创建单个OVS交换机
    switch1 = net.addSwitch('s1', cls=OVSSwitch)
    
    
    # 创建2个主机
    host1 = net.addHost('h1', cls=Host, ip='192.168.0.1/24', defaultRoute='via 192.168.0.254')
    host2 = net.addHost('h2', cls=Host, ip='192.168.0.2/24', defaultRoute='via 192.168.0.254')
   
    
    # 连接主机到交换机
    net.addLink(host1, switch1)
    net.addLink(host2, switch1)
      
        
    # 启动网络
    net.start()
      
    
    # 在OVS交换机上添加静态流表
    switch1.cmd('ovs-ofctl add-flow s1 in_port=1,actions=output:2')
    switch1.cmd('ovs-ofctl add-flow s1 in_port=2,actions=output:1')
    
    
    # 构建拓扑图
    G = nx.DiGraph()
    for switch in net.switches:
        G.add_node(switch.name)
    for host in net.hosts:
        G.add_node(host.name)
    for link in net.links:
        G.add_edge(link.intf1.node.name, link.intf2.node.name)
    
    # 保存拓扑图
    nx.draw(G, with_labels=True, node_size=1000, node_color='lightblue', font_weight='bold')
    plt.savefig('topology1.png')
    
    plt.show() # 显示网络拓扑
    
    # 打开命令行界面
    CLI(net)
    
    # 关闭网络
    net.stop()

if __name__ == '__main__':
    create_network()

运行以及测试``
2多ovs上多主机之间的通信
使用2_3_1.py代码修改成如下图2的拓扑结构
代码：

from mininet.net import Mininet
from mininet.node import OVSSwitch, Host
from mininet.cli import CLI
from mininet.link import Link
import networkx as nx
import matplotlib.pyplot as plt

def create_network():
 net = Mininet()
     # 创建单个OVS交换机
 switch1 = net.addSwitch('s1', cls=OVSSwitch)
 switch2 = net.addSwitch('s2', cls=OVSSwitch)
 
 
 # 创建2个主机
 host1 = net.addHost('h1', cls=Host, ip='192.168.0.1/24', defaultRoute='via 192.168.0.254')
 host2 = net.addHost('h2', cls=Host, ip='192.168.0.2/24', defaultRoute='via 192.168.0.254')
 host3 = net.addHost('h3', cls=Host, ip='192.168.0.3/24', defaultRoute='via 192.168.0.254')
 host4 = net.addHost('h4', cls=Host, ip='192.168.0.4/24', defaultRoute='via 192.168.0.254')


 
 # 连接主机到交换机
 net.addLink(host1, switch1)
 net.addLink(host2, switch1)
 net.addLink(host3, switch2)
 net.addLink(host4, switch2)
#交换机连接交换机
 net.addLink(switch1, switch2)

   
     
 # 启动网络
 net.start()
   
 
 # 在OVS交换机上添加静态流表
 switch1.cmd('ovs-ofctl add-flow s1 in_port=1,actions=output:2,3')
 switch1.cmd('ovs-ofctl add-flow s1 in_port=2,actions=output:1,3')
 switch1.cmd('ovs-ofctl add-flow s1 in_port=3,actions=output:1,2')
 switch2.cmd('ovs-ofctl add-flow s2 in_port=1,actions=output:2,3')
 switch2.cmd('ovs-ofctl add-flow s2 in_port=2,actions=output:1,3')
 switch2.cmd('ovs-ofctl add-flow s2 in_port=3,actions=output:1,2')
 
 # 构建拓扑图
 G = nx.DiGraph()
 for switch in net.switches:
     G.add_node(switch.name)
 for host in net.hosts:
     G.add_node(host.name)
 for link in net.links:
     G.add_edge(link.intf1.node.name, link.intf2.node.name)
 
 # 保存拓扑图
 nx.draw(G, with_labels=True, node_size=1000, node_color='lightblue', font_weight='bold')
 plt.savefig('topology1.png')
 
 plt.show() # 显示网络拓扑
 
 # 打开命令行界面
 CLI(net)
 
 # 关闭网络
 net.stop()

if __name__ == '__main__':
 create_network()

多个ovs时需要加入arp泛洪流允许
在交换机上允许arp广播流（请求和回复，跨交换机时如果arp包没有通过，一般每个ovs都需要来回）
s1.cmd(‘ovs-ofctl add-flow s1 table=0,priority=100,dl_type=0x0806,nw_proto=1,actions=flood’)
s1.cmd(‘ovs-ofctl add-flow s1 table=0,priority=100,dl_type=0x0806,nw_proto=2,actions=flood’)

使用静态流表优点是即使当前网络存在环路（假设给两个交换机之间增加一条链路，也不会产生广播风暴，流量的转发完全按照人为设定的流表转发。缺点是当节点增加时，流表配置工作量剧增。