实验2：Open vSwitch虚拟交换机实践

（一）基本要求
1、测试p0和p1的连通性。

2、执行pingall命令

查看ovs流表

抓包

（二）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()

执行结果

（三）实验心得
本次的实验难度不大，按照老师给的命令提示，都能完成。进阶部分参考资料，然后在细节上更改就行。
问题1：注意端口，如果跟老师的不一样，后面的命令要进行修改。
问题2：单独执行sudo ovs-vsctl add-port ovs-switch000 p0时，会报错could not open network device p0 (No such device)，按照老师的提示继续执行后续命令后，通过ovs-vsctl show命令就会发现错误消失。
问题3：抓包时，要先把wireshark打开，否则抓不到包。
通过这次实验，能够通过命令行终端使用OVS命令操作Open vSwitch交换机，管理流表，以及通过Python代码运行OVS命令，控制网络拓扑中的Open vSwitch交换机。