实验2：Open vSwitch虚拟交换机实践

（一）基础要求
执行ovs-vsctl show命令、以及p0和p1连通性测试的执行结果截图


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


（二）进阶要求
代码部分：
`#!/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='10.0.0.0/8')

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

CLI(net)
net.stop()

if name == 'main':
setLogLevel( 'info' )
myNetwork()

`
运行截图：

（三）个人总结
在进行这个实验的时候，会遇到一些问题，需要反复去尝试，才能找到问题发现答案。比如
1）第一遍可以运行.py文件，第二遍就运行不了，我起先以为是mininet缓存了，我执行sudo mn --clean命令清空缓存，再运行.py还是不行，后面我发现是主机与交换机之间的端口号写反了，换回来后，再执行sudo mn --clean命令就可以运行.py文件了。
2）在下发流表的时候要注意先运行.py文件进入CLI，然后再打开一个新的terminal界面去运行下发流表的命令，才能进行成功。
3）正确的使用wireshark抓包。要先开启抓包，再pingall。
wireshark的命令
sudo apt-get install wireshark //下载抓包
sudo apt-get update //下载抓包
sudo wireshark //执行抓包
下载完抓包后，后面只需要执行抓包即可。