一、基础要求

1、使用 tcpdump 验证Hub模块

h1 ping h2

2、使用 tcpdump 验证Switch模块

L2_learning模块代码流程图

h1 ping h2

h1 ping h3

二、进阶要求

1、重新搭建（一）的拓扑，此时交换机内无流表规则，拓扑内主机互不相通；编写Python程序自定义一个POX模块SendFlowInSingle3，并且将拓扑连接至SendFlowInSingle3（默认端口6633），实现向s1发送流表规则使得所有主机两两互通。

from pox.core import core

import pox.openflow.libopenflow_01 as of



class SendFlowInSingle3(object):

    def __init__ (self):

        core.openflow.addListeners(self)

    def _handle_ConnectionUp(self, event):

        msg = of.ofp_flow_mod()  

        msg.priority = 1

        msg.match.in_port = 1

        msg.actions.append(of.ofp_action_output(port=2)) 

        msg.actions.append(of.ofp_action_output(port=3))

        event.connection.send(msg)

        msg = of.ofp_flow_mod()  

        msg.priority = 1

        msg.match.in_port = 2  

        msg.actions.append(of.ofp_action_output(port=1)) 

        msg.actions.append(of.ofp_action_output(port=3))  

        event.connection.send(msg)

        msg = of.ofp_flow_mod()  

        msg.priority = 1

        msg.match.in_port = 3  

        msg.actions.append(of.ofp_action_output(port=1)) 

        msg.actions.append(of.ofp_action_output(port=2))  

        event.connection.send(msg)

def launch():

    core.registerNew(SendFlowInSingle3)

2、基于进阶1的代码，完成ODL实验的硬超时功能。

import pox.openflow.libopenflow_01 as of

class SendFlowInSingle3(object):

    def __init__(self):

        core.openflow.addListeners(self)

    def _handle_ConnectionUp(self, event):

        msg = of.ofp_flow_mod() 

        msg.priority = 1

        msg.match.in_port = 1  

        msg.actions.append(of.ofp_action_output(port=2))  

       # msg.actions.append(of.ofp_action_output(port=3)) 

        event.connection.send(msg)

        msg = of.ofp_flow_mod() 

        msg.priority = 1

        msg.match.in_port = 2  

        msg.actions.append(of.ofp_action_output(port=1))  

        msg.actions.append(of.ofp_action_output(port=3))  

        event.connection.send(msg)

        msg = of.ofp_flow_mod()  

        msg.priority = 1

        msg.match.in_port = 3  

       # msg.actions.append(of.ofp_action_output(port=1))  

        msg.actions.append(of.ofp_action_output(port=2))  

        event.connection.send(msg)

def launch():

    core.registerNew(SendFlowInSingle3)

三、个人总结

1.本次实验难度较大，L2_learning模块代码是全英文的，对我来说阅读起来很有难度。在验证Hub/Switch模块的过程中，不仅帮助我理解了POX控制器的工作原理，而且让我对于流表下发、交换机工作原理等知识更加熟悉。
2.进阶部分要自己写代码挺难的，好在在同学帮助和查阅互联网勉强写出来了。