实验2：Open vSwitch虚拟交换机实践

（一）基本要求
1.ovs-vsctl基础操作实践：创建OVS交换机。

2.在创建的交换机上增加端口p0和p1

3.创建虚拟网络空间ns0

4.创建虚拟网络空间ns1

5.最后测试p0和p1的连通性

（二）Mininet搭建的SDN拓扑

1. 自定义拓扑
   
   运行拓扑
   

2. 划分VLAN
   

3.下发流表与查看

4.主机连通性要求

（三）进阶要求

#!/usr/bin/python

from mininet.node import CPULimitedHost, Host, Node
from mininet.node import OVSKernelSwitch, UserSwitch
from mininet.net import Mininet
from mininet.node import Controller, RemoteController, OVSController
from mininet.node import IVSSwitch
from mininet.cli import CLI
from mininet.log import setLogLevel, info
from mininet.link import TCLink, Intf
from subprocess import call
 
def myNet():
 
    net = Mininet( topo=None,
                   build=False,
                   ipBase='10.0.0.0/8')
 
    info( '*** Adding controller\n' )
    c0=net.addController(name='c0',
                      controller=Controller,
                      ip='127.0.0.1',
                      protocol='OpenFlow13',
                      port=6653)
 
    info( '*** Add hosts\n')
    h1 = net.addHost('h1', cls=Host, ip='10.0.0.1', defaultRoute=None)
    h2 = net.addHost('h2', cls=Host, ip='10.0.0.2', defaultRoute=None)
    h3 = net.addHost('h3', cls=Host, ip='10.0.0.3', defaultRoute=None)
    h4 = net.addHost('h4', cls=Host, ip='10.0.0.4', defaultRoute=None)
    
    info( '*** Add switches\n')
    s1 = net.addSwitch('s1', cls=OVSKernelSwitch)
    s2 = net.addSwitch('s2', cls=OVSKernelSwitch)
 
    info( '*** Add links\n')
    net.addLink(h1, s1, 1, 1)
    net.addLink(h2, s1, 1, 2)
    net.addLink(h3, s2, 1, 1)
    net.addLink(h4, s2, 1, 2)
    net.addLink(s1, s2, 3, 3)
 
    info( '*** Starting network\n')
    net.build()

    info( '*** Starting controllers\n')
    for controller in net.controllers:
        controller.start()
 
    info( '*** Starting switches\n')
    net.get('s1').start([c0])
    net.get('s2').start([c0])
 
    info( '*** Post configure switches and hosts\n')
    s1.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096-\>vlan_vid,output:3')
    s1.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,in_port=2,actions=push_vlan:0x8100,set_field:4097-\>vlan_vid,output:3')
    s1.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,dl_vlan=0,actions=pop_vlan,output:1')
    s1.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,dl_vlan=1,actions=pop_vlan,output:2')
 
    s2.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s2 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096-\>vlan_vid,output:3')
    s2.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s2 priority=1,in_port=2,actions=push_vlan:0x8100,set_field:4097-\>vlan_vid,output:3')
    s2.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s2 priority=1,dl_vlan=0,actions=pop_vlan,output:1')
    s2.cmd('sudo ovs-ofctl -O OpenFlow13 add-flow s2 priority=1,dl_vlan=1,actions=pop_vlan,output:2')
 
    info( "*** Running test\n" )
    h1.cmdPrint( 'ping -c 3 ' + h4.IP() )
    h1.cmdPrint( 'ping -c 3 ' + h3.IP() )
    h2.cmdPrint( 'ping -c 3 ' + h4.IP() )
    h2.cmdPrint( 'ping -c 3 ' + h3.IP() )
    h3.cmdPrint( 'ping -c 3 ' + h2.IP() )
    h3.cmdPrint( 'ping -c 3 ' + h1.IP() )
    h4.cmdPrint( 'ping -c 3 ' + h2.IP() )
    h4.cmdPrint( 'ping -c 3 ' + h1.IP() )

    CLI(net)
    net.stop()
 
if __name__ == '__main__':
    setLogLevel( 'info' )
    info( '*** Scratch network demo (kernel datapath)\n' )
    Mininet.init()
    myNet()

个人总结
1.在使用ubuntu20.04中使用WIRESHARK打开之后会出现如下问题
使用解决方法

sudo groupadd wireshark
sudo chgrp wireshark /usr/bin/dumpcap
sudo chmod 4755 /usr/bin/dumpcap
sudo gpasswd -a xhz wireshark

2.下发流表时，应该在开启Mininet CLI的同时，再开启一个新终端使用OVS命令。

3.进阶要求作业时，想要运行topo.py，但会出现错误，原因是重复构建了相同的拓扑，我先前直接用命令行创建了一个拓扑结构，没有清除，所以若在.py文件中构建相同的拓扑图时需要先清除掉先前的拓扑结构。

sudo mn -c