实验2：Open vSwitch虚拟交换机实践

（一）基本要求

a) /home/用户名/学号/lab2/目录下执行ovs-vsctl show命令、以及p0和p1连通性测试的执行结果截图；


b) /home/用户名/学号/lab2/目录下开启Mininet CLI并执行pingall命令的截图、上述目录下查看OVS流表的命令结果截图，wireshark抓包截图，其余文字请勿赘述，否则扣分；

（二）进阶要求

阅读SDNLAB实验使用Mininet，编写Python代码，生成（一）中的SDN拓扑，并在代码中直接使用OVS命令，做到可以直接运行Python程序完成和（一）相同的VLAN划分。
a） 代码

#!/usr/bin/env python

from mininet.net import Mininet
from mininet.node import Controller, RemoteController, OVSController
from mininet.node import CPULimitedHost, Host, Node
from mininet.node import OVSKernelSwitch, UserSwitch
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 myNetwork():

   net = Mininet( topo=None,
                  build=False,
                  ipBase='10.0.0.1/24')

   info( '*** Adding controller\n' )
   c0=net.addController(name='c0',
                     controller=Controller,
                     protocol='tcp',
                     port=6633)

   info( '*** Add switches\n')
   s1 = net.addSwitch('s1', cls=OVSKernelSwitch)
   s2 = net.addSwitch('s2', cls=OVSKernelSwitch)

   info( '*** Add hosts\n')
   h1 = net.addHost('h1', cls=Host, ip='10.0.0.1/24', defaultRoute=None)
   h2 = net.addHost('h2', cls=Host, ip='10.0.0.2/24', defaultRoute=None)
   h3 = net.addHost('h3', cls=Host, ip='10.0.0.3/24', defaultRoute=None)
   h4 = net.addHost('h4', cls=Host, ip='10.0.0.4/24', defaultRoute=None)

   info( '*** Add links\n')
   net.addLink(h1, s1, 1, 1)
   net.addLink(s1, h2, 2, 1)
   net.addLink(s1, s2, 3, 3)
   net.addLink(s2, h3, 1, 1)
   net.addLink(s2, h4, 2, 1)

   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')

   CLI(net)
   net.stop()

if __name__ == '__main__':
   setLogLevel( 'info' )
   myNetwork()

b) 运行结果

（三）个人总结

1.一开始为交换机命名的时候“ovs-switch学号”会报错，得改为“ovs-学号”；
2.重复复制代码的时候要注意区分虚拟网络和交换机以及各种端口名称，如“ns0，ns1；s1，s2”；
3.这次实验依据实验内容的步骤较为容易实现，重点在于学习VLAN的作用和对于ovs交换机的指令，学习到了下发流表，设置VLAN ID，抓包等操作，学习到很多新内容。