old_contents: #!/usr/bin/python
  
  """
  Create a 1024-host network, and run the CLI on it.
  If this fails because of kernel limits, you may have
  to adjust them, e.g. by adding entries to /etc/sysctl.conf
  and running sysctl -p. Check util/sysctl_addon.
  """
  
  from mininet.cli import CLI
  from mininet.log import setLogLevel
  from mininet.node import OVSKernelSwitch
  from mininet.topolib import TreeNet
  
  if __name__ == '__main__':
      setLogLevel( 'info' )
      network = TreeNet( depth=2, fanout=32, switch=OVSKernelSwitch )
      network.run( CLI, network )
  
new_contents: #!/usr/bin/python
  
  """
  Create a 1024-host network, and run the CLI on it.
  If this fails because of kernel limits, you may have
  to adjust them, e.g. by adding entries to /etc/sysctl.conf
  and running sysctl -p. Check util/sysctl_addon.
  """
  
  from mininet.cli import CLI
  from mininet.log import setLogLevel
  from mininet.node import OVSSwitch
  from mininet.topolib import TreeNet
  
  if __name__ == '__main__':
      setLogLevel( 'info' )
      network = TreeNet( depth=2, fanout=32, switch=OVSSwitch )
      network.run( CLI, network )
  
subject: Change to OVSSwitch