2019 SDN上机第二次作业

1.利用mininet创建如下拓扑，要求拓扑支持OpenFlow 1.3协议，主机名、交换机名以及端口对应正确，请给出拓扑Mininet执行结果，展示端口连接情况

(1)搭建如下拓扑

(2)python脚本代码

from mininet.topo import Topo
 
class Topo2( Topo ):
 
    def __init__( self ):
 
        # Initialize topology
        Topo.__init__( self )

        # add switches and hosts  
        sw1 = self.addSwitch('s1')
        sw2 = self.addSwitch('s2')

        h1 = self.addHost('h1')
        h2 = self.addHost('h2')
        h3 = self.addHost('h3')
        h4 = self.addHost('h4')
        h5 = self.addHost('h5')
        h6 = self.addHost('h6')

        # add links
        self.addLink(h1,sw1,1,1)
        self.addLink(h2,sw1,1,2)
        self.addLink(h3,sw1,1,3)
        self.addLink(sw1,sw2,4,4)
        self.addLink(h4,sw2,1,1)
        self.addLink(h5,sw2,1,2)
        self.addLink(h6,sw2,1,3)

topos = { 'mytopo': ( lambda: Topo2() ) }

(3)执行python脚本创建mininet网络拓扑

sudo mn --custom ./fattree2.py --topo mytopo --switch ovsk,protocols=OpenFlow13

输入net查看网络拓扑

输入pingall查看节点连接情况

2. 直接在Open vSwitch下发流表，实现如下连通性要求，请逐条说明所下发的流表含义

下面三条命令分别是将h1，h2，h3三个主机进入的包转打上vlan tag，转发到s1的四号端口号，in_port是指进来的端口号，actions指的是要进行的动作，set field值为4096+vlan_id，priority是优先级。

sudo ovs-ofctl add-flow -O OpenFlow13 s1 in_port=1,priority=1,actions=push_vlan:0x8100,set_field:4096-\>vlan_vid,output:4
sudo ovs-ofctl add-flow -O OpenFlow13 s1 in_port=2,priority=1,actions=push_vlan:0x8100,set_field:4097-\>vlan_vid,output:4
sudo ovs-ofctl add-flow -O OpenFlow13 s1 in_port=3,priority=1,actions=push_vlan:0x8100,set_field:4098-\>vlan_vid,output:4

下面三条命令分别是将h4，h5，h6三个主机进入的包转打上vlan tag，转发到s2的四号端口号，in_port是指进来的端口号，actions指的是要进行的动作，set field值为4096+vlan_id，priority是优先级。

sudo ovs-ofctl add-flow -O OpenFlow13 s2 in_port=1,priority=1,actions=push_vlan:0x8100,set_field:4096-\>vlan_vid,output:4
sudo ovs-ofctl add-flow -O OpenFlow13 s2 in_port=2,priority=1,actions=push_vlan:0x8100,set_field:4097-\>vlan_vid,output:4
sudo ovs-ofctl add-flow -O OpenFlow13 s2 in_port=3,priority=1,actions=push_vlan:0x8100,set_field:4098-\>vlan_vid,output:4

下面三条命令是将从之前打上的包vlan tag的包去除vlan tag，然后根据tag进行转发

sudo ovs-ofctl -O Openflow13 add-flow s1 priority=1,dl_vlan=0,actions=pop_vlan,output:1
sudo ovs-ofctl -O Openflow13 add-flow s1 priority=1,dl_vlan=1,actions=pop_vlan,output:2
sudo ovs-ofctl -O Openflow13 add-flow s1 priority=1,dl_vlan=2,actions=pop_vlan,output:3

3. 直接在Open vSwitch查看流表，提交OVS命令执行结果

输入sudo ovs-ofctl -O OpenFlow13 dump-flows s1命令查看s1流表

同样，输入sudo ovs-ofctl -O OpenFlow13 dump-flows s2命令查看s2流表

4. 提交主机连通性测试结果，验证流表的有效性

输入pingall命令查看连通性测试结果，如下图可知h1仅和h4相连，h2仅和h5相连，h3仅和h6相连，流表有效

5. 利用Wireshark抓包，分析验证特定报文

通过sudo wireshark打开Wireshark,然后选择s1-eth4端口进行报文抓取，抓包情况如下