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

使用python脚本设计拓扑，代码如下

from mininet.topo import Topo
class MyTopo(Topo):
    def __init__(self):
        # initilaize topology
        Topo.__init__(self)
        # add hosts and switches
        host1 = self.addHost('h1')
        host2 = self.addHost('h2')
        host3 = self.addHost('h3')
        host4 = self.addHost('h4')
    host5 = self.addHost('h5')
        host6 = self.addHost('h6')
        switch1 = self.addSwitch('s1')
        switch2 = self.addSwitch('s2')
        # add links
        self.addLink(host1, switch1, 1, 1)
        self.addLink(host2, switch1, 1, 2)
    self.addLink(host3, switch1, 1, 3)
        self.addLink(host4, switch2, 1, 1)
        self.addLink(host5, switch2, 1, 2)
    self.addLink(host6, switch2, 1, 3)
    self.addLink(switch1, switch2, 4, 4)      
topos = {'mytopo': (lambda: MyTopo())}

运行指令及代码如下

连通性测试为

2.直接在Open vSwitch下发流表，用vlan得到下列虚拟网段，请逐条说明所下发的流表含义

将主机1，2，3进入s1的包打上vlan tag，转发端口4

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

将从端口4的包去除vlan tag，并根据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

将主机4，5，6进入s2的包打上vlan tag，转发端口4

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

将从端口4的包去除vlan tag，并根据tag进行转发

sudo ovs-ofctl -O OpenFlow13 add-flow s2 priority=1,dl_vlan=0,actions=pop_vlan,output:1
sudo ovs-ofctl -O OpenFlow13 add-flow s2 priority=1,dl_vlan=1,actions=pop_vlan,output:2
sudo ovs-ofctl -O OpenFlow13 add-flow s2 priority=1,dl_vlan=2,actions=pop_vlan,output:3