(一)

运行截图：
sdn第六次实践作业_python

tcpdump验证过程：
sdn第六次实践作业_github_02
（h2和h3都收到了h1的数据包）

分析：L2 Switch模块和POX的hub无太大区别，都是使用OFPP_FLOOD标记让数据包向所有端口发送，本质是集线器

(二)进阶

还没搞

心得体会

RYU的安装代码参考：

git clone https://github.com/faucetsdn/ryu.git
cd ryu
sudo pip3 install -r tools/pip-requires -i https://pypi.tuna.tsinghua.edu.cn/simple
sudo python3 setup.py install

L2Switch源码

from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_0

class L2Switch(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(L2Switch, self).__init__(*args, **kwargs)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    def packet_in_handler(self, ev):
        msg = ev.msg
        dp = msg.datapath
        ofp = dp.ofproto
        ofp_parser = dp.ofproto_parser

        actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]

        data = None
        if msg.buffer_id == ofp.OFP_NO_BUFFER:
             data = msg.data

        out = ofp_parser.OFPPacketOut(
            datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
            actions=actions, data = data)
        dp.send_msg(out)

遇到困难：可视化拓扑图光秃秃的只有一个交换机
原因：本来就只能显示交换机。和ODL不一样。尴尬