網路拓撲：

模擬結果：

python程式碼：

#!/usr/bin/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' )
    info( '*** Add switches\n')
    r3 
 
= net.addHost('r3', cls=Node, ip='0.0.0.0')
    r3.cmd('sysctl -w net.ipv4.ip_forward=1')
    r1 = net.addHost('r1', cls=Node, ip='0.0.0.0')
    r1.cmd('sysctl -w net.ipv4.ip_forward=1')
    r2 = net.addHost('r2', cls=Node, ip='0.0.0.0')
    r2.cmd('sysctl -w net.ipv4.ip_forward=1')

    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)

    info( '*** Add links\n')
    net.addLink(h1, r1)
    net.addLink(r1, r2)
    net.addLink(r2, r3)
    net.addLink(r3, h2)
    

    info( '*** Starting network\n')
    net.build()
    info( '*** Starting controllers\n')
    for controller in net.controllers:
        controller.start()

    info( '*** Starting switches\n')

    info( '*** Post configure switches and hosts\n')
    h1.cmd('ifconfig h1-eth0 192.168.10.1/24')

    r1.cmd('ifconfig r1-eth0 192.168.10.2/24')
    r1.cmd('ifconfig r1-eth1 192.168.20.2/24')

    r2.cmd('ifconfig r2-eth0 192.168.20.1/24')
    r2.cmd('ifconfig r2-eth1 192.168.30.1/24')

    r3.cmd('ifconfig r3-eth0 192.168.30.2/24')
    r3.cmd('ifconfig r3-eth1 192.168.40.2/24')

    h2.cmd('ifconfig h2-eth0 192.168.40.1/24')

    h1.cmd('route add default gw 192.168.10.2')
    h2.cmd('route add default gw 192.168.40.2')

    r1.cmd('route add -net 192.168.30.0/24 gw 192.168.20.1')
    r1.cmd('route add -net 192.168.40.0/24 gw 192.168.20.1')

    r3.cmd('route add -net 192.168.10.0/24 gw 192.168.30.1')
    r3.cmd('route add -net 192.168.20.0/24 gw 192.168.30.1')

    r2.cmd('route add -net 192.168.10.0/24 gw 192.168.20.2')
    r2.cmd('route add -net 192.168.40.0/24 gw 192.168.30.2')

    CLI(net)
    net.stop()

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

 info( '*** Add links\n')
    net.addLink(h1, r1)
    net.addLink(r1, r2)
    net.addLink(r2, r3)
    net.addLink(r3, h2)


# 當節點比較多的時候，注意連線的順序，它直接決定了對應xx-ethx位於節點左右的順序！