Mininet系列实验（七）：Mininet脚本实现控制交换机行为
1 实验目的
- 熟悉Mininet自定义拓扑脚本的编写；
- 掌握使用“ovs-vsctl”命令直接控制Open vSwitch。
2 实验原理
在SDN环境中，控制器可以通过对交换机下发流表操作来控制交换机的转发行为。在本实验中，使用Mininet基于python的脚本，调用“ovs-vsctl”命令直接控制Open vSwitch。
3 实验任务
本实验在基于Mininet脚本的不同拓扑环境下使用OpenDaylight控制交换机行为。任务一：一台交换机两台主机，从1端口进入的数据流转发到2端口，从2端口进入的数据流转发到1端口；任务二：两台交换机两台主机，主机0连接交换机0，主机1连接交换机1，交换机0连接交换机1，数据转发端口同任务一；任务三：与任务二类似，但是在创建link的时候，设置带宽、延迟以及丢包率。
任务一：一台交换机两台主机，实现从1端口进入的数据流转发到2端口，从2端口进入的数据流转发到1端口。
还是那个流程：
打开mininet文件夹——创建mymininet1.py——编辑脚本保存——改为可执行——清内存——开发者模式内打开
# !/usr/bin/python
from mininet.net import Mininet
from mininet.node import Node
from mininet.link import Link
from mininet.log import setLogLevel, info
from mininet.util import quietRun
# 调用Mininet相关模块
from time import sleep
# 调用sleep模块
def scratchNet( cname='controller', cargs='-v ptcp:' ):
"Create network from scratch using Open vSwitch."
# 创建网络节点其中有两个主机，一个交换机，一个控制器
info( "*** Creating nodes\n" )
controller = Node( 'c0', inNamespace=False )
switch0 = Node( 's0', inNamespace=False )
h0 = Node( 'h0' )
h1 = Node( 'h1' )
# 创建网络连接，分别是h0-s0和h1-s0
info( "*** Creating links\n" )
Link( h0, switch0 )
Link( h1, switch0 )
# 设置主机的IP地址，然后再诊断的同时打印出string化的h0h1
info( "*** Configuring hosts\n" )
h0.setIP( '192.168.123.1/24' )
h1.setIP( '192.168.123.2/24' )
info( str( h0 ) + '\n' )
info( str( h1 ) + '\n' )
# 开启控制器和s0的链路
info( "*** Starting network using Open vSwitch\n" )
controller.cmd( cname + ' ' + cargs + '&' )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.cmd( 'ovs-vsctl add-br dp0' )
# 在交换机的信息库里面依次打出信息
for intf in switch0.intfs.values():
print intf
print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf )
switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.8:6633' )
switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=1 actions=output:2\"' )
switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=2 actions=output:1\"' )
# 等待连接的小程序
info( '*** Waiting for switch to connect to controller' )
while 'is_connected' not in quietRun( 'ovs-vsctl show' ):
sleep( 1 )
info( '.' )
info( '\n' )
# 两个互ping6次
info( "*** Running test\n" )
h0.cmdPrint( 'ping -c6 ' + h1.IP() )
h1.cmdPrint( 'ping -c6 ' + h0.IP() )
# 关闭这个网络
info( "*** Stopping network\n" )
controller.cmd( 'kill %' + cname )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.deleteIntfs()
info( '\n' )
# 主函数部分，设置打印等级，还有调用以上的一些函数
if __name__ == '__main__':
setLogLevel( 'info' )
info( '*** Scratch network demo (kernel datapath)\n' )
Mininet.init()
scratchNet() 
任务二：两台交换机两台主机，主机0连接交换机0，主机1连接交换机1，交换机0连接交换机1，数据转发端口要求同任务一。
和前者的脚本大同小异，这里就解释mymininet1.py没有的，print switch0.cmd( 'ovs-ofctl show dp0' )意思就是打出关于s0的信息
#!/usr/bin/python
from mininet.net import Mininet
from mininet.node import Node
from mininet.link import Link
from mininet.log import setLogLevel, info
from mininet.util import quietRun
from time import sleep
def scratchNet( cname='controller', cargs='-v ptcp:' ):
"Create network from scratch using Open vSwitch."
info( "*** Creating nodes\n" )
controller = Node( 'c0', inNamespace=False )
switch0 = Node( 's0', inNamespace=False )
switch1 = Node( 's1', inNamespace=False )
h0 = Node( 'h0' )
h1 = Node( 'h1' )
info( "*** Creating links\n" )
Link( h0, switch0 )
Link( h1, switch1 )
Link( switch0, switch1 )
info( "*** Configuring hosts\n" )
h0.setIP( '192.168.123.1/24' )
h1.setIP( '192.168.123.2/24' )
info( str( h0 ) + '\n' )
info( str( h1 ) + '\n' )
info( "*** Starting network using Open vSwitch\n" )
controller.cmd( cname + ' ' + cargs + '&' )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.cmd( 'ovs-vsctl add-br dp0' )
switch1.cmd( 'ovs-vsctl del-br dp1' )
switch1.cmd( 'ovs-vsctl add-br dp1' )
for intf in switch0.intfs.values():
print intf
print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf )
for intf in switch1.intfs.values():
print intf
print switch1.cmd( 'ovs-vsctl add-port dp1 %s' % intf )
switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.8:6633' )
switch1.cmd( 'ovs-vsctl set-controller dp1 tcp: 10.0.0.8:6633' )
switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=1 actions=output:2\"' )
switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=2 actions=output:1\"' )
switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=1 actions=output:2\"' )
switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=2 actions=output:1\"' )
info( '*** Waiting for switch to connect to controller' )
while 'is_connected' not in quietRun( 'ovs-vsctl show' ):
sleep( 1 )
info( '.' )
info( '\n' )
print switch0.cmd( 'ovs-ofctl show dp0' )
print switch1.cmd( 'ovs-ofctl show dp1' )
info( "*** Running test\n" )
h0.cmdPrint( 'ping -c3 ' + h1.IP() )
h1.cmdPrint( 'ping -c3 ' + h0.IP() )
info( "*** Stopping network\n" )
controller.cmd( 'kill %' + cname )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.deleteIntfs()
switch1.cmd( 'ovs-vsctl del-br dp1' )
switch1.deleteIntfs()
info( '\n' )
if __name__ == '__main__':
setLogLevel( 'info' )
info( '*** Scratch network demo (kernel datapath)\n' )
Mininet.init()
scratchNet()
任务三：与任务二类似，但是在创建link的时候，设置带宽、延迟以及丢包率。
#!/usr/bin/python
from mininet.net import Mininet
from mininet.node import Node
from mininet.link import TCLink
from mininet.log import setLogLevel, info
from mininet.util import quietRun
from time import sleep
def scratchNet( cname='controller', cargs='-v ptcp:' ):
"Create network from scratch using Open vSwitch."
info( "*** Creating nodes\n" )
controller = Node( 'c0', inNamespace=False )
switch0 = Node( 's0', inNamespace=False )
switch1 = Node( 's1', inNamespace=False )
h0 = Node( 'h0' )
h1 = Node( 'h1' )
info( "*** Creating links\n" )
linkopts0=dict(bw=10)
linkopts1=dict(bw=10, delay='5ms', loss=10)
TCLink( h0, switch0,**linkopts0)
TCLink( h1, switch1,**linkopts0)
TCLink( switch0, switch1,**linkopts1)
info( "*** Configuring hosts\n" )
h0.setIP( '192.168.123.1/24' )
h1.setIP( '192.168.123.2/24' )
info( str( h0 ) + '\n' )
info( str( h1 ) + '\n' )
info( "*** Starting network using Open vSwitch\n" )
controller.cmd( cname + ' ' + cargs + '&' )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.cmd( 'ovs-vsctl add-br dp0' )
switch1.cmd( 'ovs-vsctl del-br dp1' )
switch1.cmd( 'ovs-vsctl add-br dp1' )
for intf in switch0.intfs.values():
print intf
print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf )
for intf in switch1.intfs.values():
print intf
print switch1.cmd( 'ovs-vsctl add-port dp1 %s' % intf )
switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.8:6633' )
switch1.cmd( 'ovs-vsctl set-controller dp1 tcp: 10.0.0.8:6633' )
switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=1 actions=output:2\"' )
switch0.cmd( 'ovs-ofctl add-flow dp0 \"in_port=2 actions=output:1\"' )
switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=1 actions=output:2\"' )
switch1.cmd( 'ovs-ofctl add-flow dp1 \"in_port=2 actions=output:1\"' )
info( '*** Waiting for switch to connect to controller' )
while 'is_connected' not in quietRun( 'ovs-vsctl show' ):
sleep( 1 )
info( '.' )
info( '\n' )
print switch0.cmd( 'ovs-ofctl show dp0' )
print switch1.cmd( 'ovs-ofctl show dp1' )
info( "*** Running test\n" )
h0.cmdPrint( 'ping -c3 ' + h1.IP() )
h1.cmdPrint( 'ping -c3 ' + h0.IP() )
info( "*** Stopping network\n" )
controller.cmd( 'kill %' + cname )
switch0.cmd( 'ovs-vsctl del-br dp0' )
switch0.deleteIntfs()
switch1.cmd( 'ovs-vsctl del-br dp1' )
switch1.deleteIntfs()
info( '\n' )
if __name__ == '__main__':
setLogLevel( 'info' )
info( '*** Scratch network demo (kernel datapath)\n' )
Mininet.init()
scratchNet() 
总结：
1.对ovs加深理解
2.能够完全看懂脚本
3.需要更深一步了解mininet的模块的函数