实验2：Open vSwitch虚拟交换机实践

基础要求

a）

执行ovs-vsctl show命令

p0和p1连通性测试的执行结果

b）

开启Mininet CLI并执行pingall命令

查看OVS流表的命令结果

wireshark抓包

进阶要求

#!/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()

执行结果

实验总结

实验难度

本次实验比第一次的更加复杂，尤其在理解下发流表命令上花费了较长的时间，但是因为有了实验一使用mininet的基础，总体感觉难度适中。

问题与解决方法：

问题1：在运行下发流表的命令时，没有把py文件先运行起来，使得流表下发失败

解决：一个终端利用Mininet CLI的custom参数加载py文件，另一个终端运行下发流表命令

问题2：抓包的时候需要pingall

实验收获：

通过本次实验我学会了ovs基础操作、下发流表、抓包以及掌握了更多python基础语法。但是一些细节还不是明白得很透彻，还有很多东西需要学习！