Lab 3: OpenFlow & Mininet

實驗描述

OpenFlow 是目前在 SDN 中，負責處理控制層 (controller) 和資料層 (switch, router...etc devices) 的溝通協定。

本次實驗讓大家使用 Mininet 快速佈署模擬 SDN 的網路環境，並且簡單操作 OpenvSwitch 來操作 flow，

最後來對 POX controller programming來達到不同的需求。

實驗環境

理學大樓 1002 教室
	Cloud-A01 ~ Cloud-D12
CPU	AMD Phenom™ II X6 1065T Processor
Memory	8G
Disk spaces	500G、500G
O.S.	Debian Wheezy

虛擬機環境
	Virtual Machine
Location	821 機房伺服器
CPU	vcpu*2
Memory	8G
Disk spaces	80G (QCOW2 Format)
O.S.	Debian Jessie

理學大樓 821 機房
	CSIE-Cloud01 ~ CSIE-Cloud06
CPU	AMD Opteron™ Processor 6128 * 2 (total 16 cpu cores)
Memory	64G
Disk spaces	500G, 500G, 1T
O.S.	Debian wheezy
	CSIE-Cloud07, CSIE-Cloud08
CPU	AMD Opteron™ Processor 6234 * 2 (total 24 cpu cores)
Memory	128G, 160G
Disk spaces	500G, 500G, 1T
O.S.	Debian wheezy

環境參數

為了避免輸入錯誤以及方便區分 IP 使用環境，我們使用下列幾個按鈕來快速取代各個不同 IP。

您的機器參數:

Username ： [USERNAME]

Code number ： [code-num]

Host IP ： [Host-IP]

Gateway ： [Gateway-IP]

安裝實作 (Mininet)

Login Server

若您使用 MS Windows, 請參閱說明 Login Server From Windows.

Open a terminal emulator and then type the following commands.

ssh [USERNAME]@cloud.cs.nchu.edu.tw -X -p [PortNUM]

安裝 Mininet 所需套件及準備工作

安裝需求套件和設定

sudo cp ~/.Xauthority /root

sudo aptitude update

sudo aptitude install python-setuptools git xterm
	The following NEW packages will be installed:
  git git-man{a} liberror-perl{a} python-setuptools rsync{a} 
0 packages upgraded, 5 newly installed, 0 to remove and 198 not upgraded.
Need to get 5,074 kB of archives. After unpacking 24.9 MB will be used.
Do you want to continue? [Y/n/?]

將需要的檔案從 github 上抓下來

 git clone git://github.com/mininet/mininet
	Cloning into 'mininet'...
remote: Counting objects: 6722, done.
remote: Compressing objects: 100% (2542/2542), done.
remote: Total 6722 (delta 4098), reused 6670 (delta 4058)
Receiving objects: 100% (6722/6722), 2.26 MiB | 239.00 KiB/s, done.
Resolving deltas: 100% (4098/4098), done.
Checking connectivity... done.

cd mininet

由於最近剛改版，但我們還是使用上一個穩定的版本，切換到2.1.0

git checkout -b 2.1.0 2.1.0 
	Switched to a new branch '2.1.0'

開始編譯和安裝 mininet

gcc -o mnexec mnexec.c

sudo mv mnexec /usr/local/bin/

sudo python setup.py install
	...

Adding setuptools 5.5.1 to easy-install.pth file
Installing easy_install script to /usr/local/bin
Installing easy_install-2.7 script to /usr/local/bin

Using /usr/lib/python2.7/dist-packages
Finished processing dependencies for mininet==2.1.0

檢查有無錯誤

echo $?
	0

測試 mininet 版本
```
sudo mn --version
	2.1.0	
	
```

建立實驗環境

用 command line 啟動 mininet

建立 1 台 Switch 和 3 台 Host 的網路拓樸環境，並等待遠端接上 OpenFlow Controller

sudo mn --topo single,3 --mac --controller remote
	*** Creating network
*** Adding controller
Unable to contact the remote controller at 127.0.0.1:6633
*** Adding hosts:
h1 h2 h3 
*** Adding switches:
s1 
*** Adding links:
(h1, s1) (h2, s1) (h3, s1) 
*** Configuring hosts
h1 h2 h3 
*** Starting controller
*** Starting 1 switches
s1 
*** Starting CLI:
mininet>

檢查網路拓樸連線狀況

net
	h1 h1-eth0:s1-eth1	
h2 h2-eth0:s1-eth2
h3 h3-eth0:s1-eth3
s1 lo:  s1-eth1:h1-eth0 s1-eth2:h2-eth0 s1-eth3:h3-eth0
c0

觀察其中一台 host 的網路狀況，我們選擇 h1

h1 ifconfig
	h1-eth0   Link encap:Ethernet  HWaddr 00:00:00:00:00:01  
          inet addr:10.0.0.1  Bcast:10.255.255.255  Mask:255.0.0.0
          inet6 addr: fe80::200:ff:fe00:1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:38 errors:0 dropped:0 overruns:0 frame:0
          TX packets:68 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2356 (2.3 KiB)  TX bytes:4048 (3.9 KiB)
...

使用指令透過 switch 中的 rule 來觀察 Openflow

實作 switch 正常行為

讓底下的 host 互相 ping

pingall
	*** Ping: testing ping reachability
h1 -> X X 
h2 -> X X 
h3 -> X X 
*** Results: 100% dropped (0/6 received)

查看 switch 中的 flow

sh ovs-ofctl dump-flows s1
	NXST_FLOW reply (xid=0x4):

插入 flow 讓 switch 正常運作

sh ovs-ofctl add-flow s1 "priority=0,action=normal"

這時候再觀察 switch 中的 flow

sh ovs-ofctl dump-flows s1
	NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=35.574s, table=0, n_packets=0, n_bytes=0, idle_age=35, priority=0 actions=NORMAL

讓底下的 host 互相 ping，此時 switch 已經正常運作

pingall
	*** Ping: testing ping reachability
h1 -> h2 h3 
h2 -> h1 h3 
h3 -> h1 h2 
*** Results: 0% dropped (6/6 received)

清除 switch 中的 flow

sh ovs-ofctl del-flows s1

為了確保 switch 中的 flow 為空，我們再 dump 一次

sh ovs-ofctl dump-flows s1
	NXST_FLOW reply (xid=0x4):

IP traffic control

首先讓 switch 能正常運作，因此再重新加入 flow

sh ovs-ofctl add-flow s1 "priority=0,action=normal"

再增加一條新的 flow 到 switch 中，讓所有目標 IP 為 10.0.0.1 的封包都作 drop 行為

sh ovs-ofctl add-flow s1 "priority=100,eth_type=0x800,ip_dst=10.0.0.1,action=drop"

此時 switch 中的 flow 規則如下

sh ovs-ofctl dump-flows s1
	NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=8.880s, table=0, n_packets=0, n_bytes=0, idle_age=8, priority=0 actions=NORMAL
 cookie=0x0, duration=3.480s, table=0, n_packets=0, n_bytes=0, idle_age=3, priority=100,ip,nw_dst=10.0.0.1 actions=drop

作 pingall 的動作，可觀察到所有往 h1 的 IP 封包都傳不過去

pingall
	*** Ping: testing ping reachability
h1 -> X X 
h2 -> X h3 
h3 -> X h2 
*** Results: 66% dropped (2/6 received)

清除 switch 中的 flow

sh ovs-ofctl del-flows s1

ARP traffic control

首先讓 switch 能正常運作，因此再重新加入 flow

sh ovs-ofctl add-flow s1 "priority=0,action=normal"

這次新增一條 flow 到 switch 中，讓所有目標 MAC address 為 00:00:00:00:00:02 的封包都作 drop 行為

sh ovs-ofctl add-flow s1 "priority=100,eth_type=0x806,dl_dst=00:00:00:00:00:02,action=drop"

作 pingall 的動作，可觀察到所有往 h2 的 ARP 封包都傳不過去

pingall
	*** Ping: testing ping reachability
h1 -> X h3 
h2 -> X X 
h3 -> h1 X 
*** Results: 66% dropped (2/6 received)

關閉 mininet

exit
	*** Stopping 1 switches
s1 ...
*** Stopping 3 hosts
h1 h2 h3 
*** Stopping 1 controllers
c0 
*** Done
completed in 5566.056 seconds

POX controller

在上一段落中，我們使用 mininet 來建立我們需要的 openflow 實驗環境，並且用指令來對 switch 作安裝 flow 的動作。

這段落我們介紹如何透過 SDN controller 達到同樣的效果，並作簡單的操作。

打開新的 terminal 並且登入到所分配的機器

ssh [USERNAME]@cloud.cs.nchu.edu.tw -X -p [PortNUM]

安裝POX
換回新開的 terminal，我們從學校伺服器抓取檔案，以節省頻寬
```
wget http://www.cs.nchu.edu.tw/~snmlab/CloudMgnt201409/pox.tar
```
解壓縮
```
tar xvf pox.tar
```
在校外可以直接上官網抓
```
git clone http://github.com/noxrepo/pox
```
```
cd ~/pox
```

測試 POX 範例

執行 layer 2 learning switch

./pox.py forwarding.l2_learning
	POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
INFO:core:POX 0.2.0 (carp) is up.
INFO:openflow.of_01:[00-00-00-00-00-01 1] connected

我們還是使用 mininet 來當作實驗環境

首先先切回 mininet 的 terminal ，並重新執行 mininet 環境

sudo mn --topo single,3 --mac --controller remote
	*** Creating network
*** Adding controller
the remote controller at 127.0.0.1:6633
*** Adding hosts:
h1 h2 h3 
*** Adding switches:
s1 
*** Adding links:
(h1, s1) (h2, s1) (h3, s1) 
*** Configuring hosts
h1 h2 h3 
*** Starting controller
*** Starting 1 switches
s1 
*** Starting CLI:

讓 host 間互 ping

pingall
	*** Ping: testing ping reachability
h1 -> h2 h3 
h2 -> h1 h3 
h3 -> h1 h2 
*** Results: 0% dropped (6/6 received)

查看 switch 中的 flow

sh ovs-ofctl dump-flows s1
	 cookie=0x0, duration=1.540s, table=0, n_packets=1, n_bytes=98, idle_timeout=10, hard_timeout=30, idle_age=1, priority=65535,icmp,in_port=1,vlan_tci=0x0000,dl_src=00:00:00:00:00:01,dl_dst=00:00:00:00:00:02,nw_src=10.0.0.1,nw_dst=10.0.0.2,nw_tos=0,icmp_type=8,icmp_code=0 actions=output:2
 cookie=0x0, duration=1.522s, table=0, n_packets=1, n_bytes=98, idle_timeout=10, hard_timeout=30, idle_age=1, priority=65535,icmp,in_port=3,vlan_tci=0x0000,dl_src=00:00:00:00:00:03,dl_dst=00:00:00:00:00:01,nw_src=10.0.0.3,nw_dst=10.0.0.1,nw_tos=0,icmp_type=0,icmp_code=0 actions=output:1
...

修改簡單防火牆功能

對 POX controller 的視窗按下 Crtl + C 暫時中斷 controller

^C
	INFO:core:Going down...
INFO:openflow.of_01:[00-00-00-00-00-01 3] disconnected
INFO:core:Down.

我們用 l2_learning.py 來作修改，首先從同一個檔案複製成不同的檔名

cd ~/pox/pox/forwarding/

ls
	hub.py        l2_flowvisor.py  l2_multi.py             l2_pairs.py
__init__.py   l2_learning.py   l2_nx.py                l3_learning.py
__init__.pyc  l2_learning.pyc  l2_nx_self_learning.py  topo_proactive.py

cp l2_learning.py l2_icmp_block.py

cp l2_learning.py l2_ip_block.py

cp l2_learning.py l2_mac_block.py

檢查檔案都有複製到檢查檔案都有複製到

ls
	hub.py           l2_icmp_block.py  l2_mac_block.py         l2_pairs.py
__init__.py      l2_ip_block.py    l2_multi.py             l3_learning.py
__init__.pyc     l2_learning.py    l2_nx.py                topo_proactive.py
l2_flowvisor.py  l2_learning.pyc   l2_nx_self_learning.py

阻擋 ICMP 封包

當我們發現是 ICMP 封包時，對其作 drop 的行為

修改 l2_icmp_block.py 在 146 行新增底下內容

nano l2_icmp_block.py -c
	# 146 行新增
    icmpPkt = packet.find('icmp')
    if icmpPkt is not None:
        log.info("Receive ICMP Packet, drop it!!")
        drop()
        return

執行 l2_icmp_block.py

~/pox/pox.py forwarding.l2_icmp_block
	POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
INFO:core:POX 0.2.0 (carp) is up.
INFO:openflow.of_01:[00-00-00-00-00-01 1] connected

在 mininet 的 terminal 做測試，這次我們讓 h1 ping h2 三次

h1 ping h2 -c 3
	PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.

--- 10.0.0.2 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2015ms

同時可以發現 POX controller 有 log 產生

INFO:forwarding.l2_icmp_block:Receive ICMP Packet, drop it!!

對 POX controller 的視窗按下 Crtl + C 暫時中斷 controller

^C
	INFO:core:Going down...
INFO:openflow.of_01:[00-00-00-00-00-01 3] disconnected
INFO:core:Down.

阻擋特定 IP 封包

當我們發現來自要阻擋的特定 IP 封包，對其作 drop 的行為

修改 l2_ip_block.pyl2_ip_block.py 在 146 行新增底下內容

nano l2_ip_block.py -c
	# 146 行新增
    IPPkt = packet.find('ipv4')
    if IPPkt is not None:
      log.info("Receive %s Packet!!",IPPkt.srcip)
      if IPPkt.srcip == '10.0.0.1':
        log.info("Drop %s Packet...",IPPkt.srcip)
        drop()
        return

執行 l2_ip_block.py

~/pox/pox.py forwarding.l2_ip_block
	POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
INFO:core:POX 0.2.0 (carp) is up.
INFO:openflow.of_01:[00-00-00-00-00-01 1] connected

在 mininet 的 terminal 做測試，這次我們讓 h1 ping h2 三次

h1 ping h2 -c 3
	PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.

--- 10.0.0.2 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 1999ms

同時可以發現 POX controller 有 log 產生

INFO:forwarding.l2_ip_block:Receive 10.0.0.1 Packet!!

INFO:forwarding.l2_ip_block:Drop 10.0.0.1 Packet
...

對 POX controller 的視窗按下 Crtl + C 暫時中斷 controller

^C
	INFO:core:Going down...
INFO:openflow.of_01:[00-00-00-00-00-01 3] disconnected
INFO:core:Down.

阻擋特定 mac address 封包

當我們發現來自要阻擋的特定 mac address 封包，對其作 drop 的行為

修改 l2_mac_block.py 在 147 行新增底下內容

nano l2_mac_block.py -c
	# 27 行新增
from pox.lib.addresses import EthAddr
# 147 行新增
    MacAddr = '00:00:00:00:00:01'
    EthPkt = packet.find('ethernet')
    if EthPkt is not None:
      log.info("%s",EthPkt.src)
      if EthPkt.src == EthAddr(MacAddr):
        log.info("Match")
        drop()
        return

執行 l2_mac_block.py

~/pox/pox.py forwarding.l2_mac_block
	POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
INFO:core:POX 0.2.0 (carp) is up.
INFO:openflow.of_01:[00-00-00-00-00-01 1] connected

在 mininet 的 terminal 做測試，這次我們讓 h1 ping h2 三次

h1 ping h2 -c 3
	PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.

--- 10.0.0.2 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 2014ms

同時可以發現 POX controller 有 log 產生

INFO:forwarding.l2_mac_block:00:00:00:00:00:01

INFO:forwarding.l2_mac_block:Match
...

對 POX controller 的視窗按下 Crtl + C 暫時中斷 controller

^C
	INFO:core:Going down...
INFO:openflow.of_01:[00-00-00-00-00-01 3] disconnected
INFO:core:Down.

Mininet 除了提供使用 command line 來建立虛擬的網路之外，也可以利用提供的 library 來建立我們想要的環境

切換到 mininet 的 terminal 視窗，關閉 mininet

exit
	*** Stopping 1 switches
s1 ...
*** Stopping 3 hosts
h1 h2 h3 
*** Stopping 1 controllers
c0 
*** Done
completed in 5566.056 seconds

前往 mininet 的 example 資料夾

cd ~/mininet/examples

建立實驗用的虛擬網路環境

nano lab3_network_subnets.py
	#!/usr/bin/python

from mininet.net import Mininet
from mininet.node import RemoteController,Host,Node
from mininet.cli import CLI
from mininet.log import setLogLevel, info

def emptyNet():

    net = Mininet( controller=RemoteController )

    info( '*** Adding controller\n' )
    net.addController( 'c0', 
                       controller=RemoteController, 
                       ip = "127.0.0.1", 
                       port=6633 )

    info( '*** Adding hosts\n' )
    #---------subnet1---------
    h1 = net.addHost( 'h1', 
                      ip='10.0.0.1', 
                      mac='00:00:00:00:00:01',
                      defaultRoute='via 10.0.0.254')
    h2 = net.addHost( 'h2', 
                      ip='10.0.0.2',
                      mac='00:00:00:00:00:02',
                      defaultRoute='via 10.0.0.254')
    h3 = net.addHost( 'h3', 
                      ip='10.0.0.3', 
                      mac='00:00:00:00:00:03',
                      defaultRoute='via 10.0.0.254')
    #---------subnet2---------
    k4 = net.addHost( 'k4', 
                      ip='192.168.0.10', 
                      mac='00:00:00:00:00:10',
                      defaultRoute='via 192.168.0.254')
    k5 = net.addHost( 'k5',
                      ip='192.168.0.11',
                      mac='00:00:00:00:00:11',
                      defaultRoute='via 192.168.0.254')
    k6 = net.addHost( 'k6', 
                      ip='192.168.0.12', 
                      mac='00:00:00:00:00:12',
                      defaultRoute='via 192.168.0.254')
        
    info( '*** Adding switch\n' )
    s1 = net.addSwitch( 's1' )
    s2 = net.addSwitch( 's2' )
    info( '*** Creating links\n' )
    #---------subnet1---------
    net.addLink( h1, s1 )
    net.addLink( h2, s1 )
    net.addLink( h3, s1 )
    #---------subnet2---------
    net.addLink( k4, s2 )
    net.addLink( k5, s2 )
    net.addLink( k6, s2 )
    #---------switch----------
    net.addLink( s1, s2 )

    info( '*** Adding gateway\n')
    gateway = Host('gateway')
    net.addLink(s1, gateway)
    net.addLink(s2, gateway)
    gateway.intf("gateway-eth0").setIP('10.0.0.254/24')
    gateway.intf("gateway-eth1").setIP('192.168.0.254/24')
    
    info( '*** Starting network\n')
    net.start()

    info( '*** Running CLI\n' )
    CLI( net )

    info( '*** Stopping network' )
    net.stop()

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

將檔案轉成可執行檔

sudo chmod +x lab3_network_subnets.py

執行檔案並我們需要的網路環境

sudo ./lab3_network_subnets.py
	*** Adding controller
Unable to contact the remote controller at 127.0.0.1:6633
*** Adding hosts
*** Adding switch
*** Creating links
*** Adding gateway
*** Starting network
*** Configuring hosts
h1 h2 h3 k4 k5 k6 
*** Starting controller
*** Starting 2 switches
s1 s2 
*** Running CLI
*** Starting CLI:
mininet>

正常的狀況而言，網路中的 switch 因為沒有任何的 flow 在裡面，所以網路不會通，此步驟可跳過，因為機器有點多耗時也多

pingall
	*** Ping: testing ping reachability
h1 -> X X X X X 
h2 -> X X X X X 
h3 -> X X X X X 
k4 -> X X X X X 
k5 -> X X X X X 
k6 -> X X X X X 
*** Results: 100% dropped (0/30 received)

切換到原本使用 POX controller 的 terminal，確定目錄為 ~/pox/pox/forwarding

cd ~/pox/pox/forwarding

先來測試看看 l3_learning 的範例

~/pox/pox.py forwarding.l3_learning --fakeways=10.0.0.254,192.168.0.254
	POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
INFO:core:POX 0.2.0 (carp) is up.
INFO:openflow.of_01:[00-00-00-00-00-02 1] connected
INFO:openflow.of_01:[00-00-00-00-00-01 2] connected

切換到 mininet 的 terminal 視窗

pingall
	*** Ping: testing ping reachability
h1 -> h2 h3 k4 k5 k6 
h2 -> h1 h3 k4 k5 k6 
h3 -> h1 h2 k4 k5 k6 
k4 -> h1 h2 h3 k5 k6 
k5 -> h1 h2 h3 k4 k6 
k6 -> h1 h2 h3 k4 k5 
*** Results: 0% dropped (30/30 received)

我們現在來增加一些簡單的 traffic control，切換回 POX 的視窗，按下 crtl + c 先中斷執行中的 controller

^c
	^CINFO:core:Going down...
INFO:openflow.of_01:[00-00-00-00-00-01 2] disconnected
INFO:openflow.of_01:[00-00-00-00-00-02 1] disconnected
INFO:core:Down.

從伺服器上抓已經修改好的檔案

wget http://www.cs.nchu.edu.tw/~snmlab/CloudMgnt201409/l3_learning_lab3.py

確認檔案存在

ls
	hub.py           l2_icmp_block.py   l2_learning.py    l2_multi.py             l3_learning_lab3.py
__init__.py      l2_icmp_block.pyc  l2_learning.pyc   l2_nx.py                l3_learning.py
__init__.pyc     l2_ip_block.py     l2_mac_block.py   l2_nx_self_learning.py  topo_proactive.py
l2_flowvisor.py  l2_ip_block.pyc    l2_mac_block.pyc  l2_pairs.py

這份檔案是由剛剛的 l3_learning 作修改，從 203 行的地方開始新增內容，若是想要手動修改的話，請注意空格對齊還有重複的部分

建議對照 l3_learning_lab3 檔案進行修改

nano -c l3_learning_lab3.py
	# 191 行新增
srcaddr = packet.next.srcip
# 203 行新增
if dstaddr == '10.0.0.1':
  msg = of.ofp_flow_mod()
  msg.match.dl_type = 0x800
  msg.match.nw_dst = IPAddr("10.0.0.1")
  event.connection.send(msg.pack())
elif srcaddr == '10.0.0.1':
  msg = of.ofp_flow_mod()
  msg.match.dl_type = 0x800
  msg.match.nw_src = IPAddr("10.0.0.1")
  event.connection.send(msg.pack())
else:
  actions = []
  actions.append(of.ofp_action_dl_addr.set_dst(mac))
  actions.append(of.ofp_action_output(port = prt))
  match = of.ofp_match.from_packet(packet, inport)
  match.dl_src = None # Wildcard source MAC
            
  msg = of.ofp_flow_mod(command=of.OFPFC_ADD,
  idle_timeout=FLOW_IDLE_TIMEOUT,
  hard_timeout=of.OFP_FLOW_PERMANENT,
  buffer_id=event.ofp.buffer_id,
  actions=actions,
  match=of.ofp_match.from_packet(packet,
                                 inport))
  event.connection.send(msg.pack())

來測試剛剛修改的 l3_learning_lab3 controller

~/pox/pox.py forwarding.l3_learning_lab3 --fakeways=10.0.0.254,192.168.0.254
	POX 0.2.0 (carp) / Copyright 2011-2013 James McCauley, et al.
INFO:core:POX 0.2.0 (carp) is up.
INFO:openflow.of_01:[00-00-00-00-00-02 1] connected
INFO:openflow.of_01:[00-00-00-00-00-01 2] connected

切換到 mininet 的 terminal 視窗，作 pingall 的動作，可以發現通往 h1 的封包都不通

pingall
	*** Ping: testing ping reachability
h1 -> X X X X X 
h2 -> X h3 k4 k5 k6 
h3 -> X h2 k4 k5 k6 
k4 -> X h2 h3 k5 k6 
k5 -> X h2 h3 k4 k6 
k6 -> X h2 h3 k4 k5 
*** Results: 33% dropped (20/30 received)

我們再來觀察目前 switch 中的 flow，可以發現來往 h1 機器的 IP 封包都會被 drop

sh ovs-ofctl dump-flows s1
	NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=66.621s, table=0, n_packets=1, n_bytes=98, idle_age=56, ip,nw_dst=10.0.0.1 actions=drop
 cookie=0x0, duration=116.643s, table=0, n_packets=4, n_bytes=392, idle_age=76, ip,nw_src=10.0.0.1 actions=drop

Assignment#3 (Deadline: before Lab4 12/24 23：59)

設計一 POX controller program，需有以下功能：

阻擋所有的 ping 10.0.0.1 的 ICMP 封包。
建立一台 mac to IP 的唯一機器。
阻擋特定兩個 IP 互相連線。
其他的網路功能則維持 L2 learning 之狀態。

由於 Lab4 實驗環境架設需做調整，故本次作業不會有 Bonus 題目，分數照常算入本次作業，

但是機器會在 12/23 的下午做更新動作，故上機的實驗機器將不再提供作業，請同學注意時間。

繳交作業方式有所變更，請寄信到助教信箱( g102056049@mail.nchu.edu.tw )，請附上姓名、機器代號和檔案位置，並且標明第 2 點和第 3 點的 IP ，

已經完成作業的同學不好意思，麻煩再寄一份檔案到我信箱。

可繳交作業時間不會改變，請同學盡速完成作業。

繳交作業時請關閉POX和Mininet，避免衝突。

作業檢查頁