实验2：Open vSwitch虚拟交换机实践

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，完成相关要求后查看网络状态与端口信息

2.使用Mininet搭建的SDN拓扑，如下图所示，要求支持OpenFlow 1.3协议，主机名、交换机名以及端口对应正确。

代码部分：

from mininet.topo import Topo

class MyTopo(Topo):

    def __init__(self):
    
        # initilaize topology
        Topo.__init__(self)
    
        # add hosts
        h1 = self.addHost('h1')
        h2 = self.addHost('h2')
        h3 = self.addHost('h3')
        h4 = self.addHost('h4')
    
        # add switches
        s1 = self.addSwitch('s1')
        s2 = self.addSwitch('s2')

        # add links
        self.addLink(h1, s1, 1, 1)
        self.addLink(h2, s1, 1, 2)
        self.addLink(h3, s2, 1, 1)
        self.addLink(h4, s2, 1, 2)
        self.addLink(s1, s2, 3, 3)
topos = {'mytopo': (lambda:MyTopo())}

运行文件，查看连接。

3.通过命令行终端输入“ovs-ofctl”命令，直接在s1和s2上添加流表，划分出所要求的VLAN。

VLAN_ID	Hosts
0	h1 h3
1	h2 h4

下发流表

查看流表

4.主机连通性要求：

• h1 – h3互通

• h2 – h4互通

• 其余主机不通

进行pingall操作，进行连通性检查

利用 sudo wireshark 命令抓包

• Mininet命令行界面输入 h1 ping h3 ，抓取的包id为0

• Mininet命令行界面输入 h1 ping h3 ，抓取的包id为1

(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(h1, s1, 1, 1)
    net.addLink(h2, s1, 1, 2)
    net.addLink(s1, s2, 3, 3)
    net.addLink(h4, s2, 1, 2)
    net.addLink(h3, s2, 1, 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])

    #添加流表，完成VLAN划分
    info("*** Send the flow table down\n\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')
    
    #查看流表
    info( "*** print the streamtable\n" )
    info( s1.cmd( 'ovs-ofctl dump-flows s1 -O OpenFlow13' ))
    info( s2.cmd( 'ovs-ofctl dump-flows s2 -O OpenFlow13' ))
    
    info( '*** Post configure switches and hosts\n')
    CLI(net)
    net.stop()

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

运行文件，连通性检查与查看VLAN划分

利用 sudo wireshark 命令抓包

• Mininet命令行界面输入 h1 ping h3 ，抓取的包id为0

• Mininet命令行界面输入 h1 ping h3 ，抓取的包id为1

(三)个人总结

所遇错误与解决方法

​ 在进行下放流表操作时，运行sudo ovs-ofctl -O OpenFlow13 add-flow s1 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096-\>vlan_vid,output:3后报错ovs-ofctl: s1 is not a bridge or a socket。

​ 在上网搜索后，有观点提出要配置交换机的数据路径类型，输入指令ovs-vsctl set bridge br0 datapath_type=netdev，问题没有得到解决，说明错误的点不一样。在尝试重启也没无效过后，发现是因为前面拓扑的运行被终止了。重新启动前面的拓扑，问题得到解决。

实验感想

​ 本次实验总体难度不大，参考ppt做下来总体很流畅（除了脑子不好+粗心导致下发流表时忘记开拓扑）。通过这次实验，学会了OVS的部分命令用法与规则，感觉挺好玩的，希望接下来学习的内容会更加有趣。