利用Python脚本完成一个Fat-tree型的拓扑

利用Python脚本完成如下图所示的一个Fat-tree型的拓扑（交换机和主机名需与图中一致，即s1_s6，h1h8）

• 参考资料
  
  
• 修改代码如下：

from mininet.topo import Topo
from mininet.net import Mininet
from mininet.node import RemoteController,CPULimitedHost
from mininet.link import TCLink
from mininet.util import dumpNodeConnections

class MyTopo( Topo ):
    "Simple topology example."

    def __init__( self ):
        "Create custom topo."

        # Initialize topology
        Topo.__init__( self )
        L1 = 2
        L2 = L1 * 2
        s = []

        # add core ovs
        for i in range( L1 ):
                sw = self.addSwitch( 's{}'.format( i + 1 ) )
                s.append( sw )

        # add aggregation ovs
        for i in range( L2 ):
                sw = self.addSwitch( 's{}'.format( i + L1 + 1 ) )
                s.append( sw )

        # add links between core and aggregation/edge ovs
        for i in range( L1 ):
		sw1 = s[i]
                for j in range( L2 ):
			sw2 = s[L1 + j]
			self.addLink( sw2, sw1 )

        #add hosts and its links with aggregation/edge ovs
        count = 1
        for sw1 in s[L1::1]:
                for i in range(2):
                	host = self.addHost( 'h{}'.format( count ) )
                	self.addLink( sw1, host )
                	count += 1
topos = { 'mytopo': ( lambda: MyTopo() ) }