2019 SDN上机第2次作业

1. 利用mininet创建拓扑，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

• Python代码：

from mininet.topo import Topo
from mininet.net import Mininet
from mininet.node import RemoteController,CPULimitedHost
from mininet.link import TCLink
from mininet.util import dumpNodeConnections
 
class MyTopo( Topo ):
    "Simple topology example."
 
    def __init__( self ):
        "Create custom topo."
 
        Topo.__init__( self )
	switchs = []
        for i in range(2):
            sw = self.addSwitch("s{}".format(i + 1))
            switchs.append(sw)
	
	self.addLink(switchs[0], switchs[1],4,4)	

	count = 1
        for sw in switchs:
            for i in range(3):
                h = self.addHost("h{}".format(count))
                self.addLink(sw, h,i+1,1)
                count += 1
        
topos = { 'mytopo': ( lambda: MyTopo() ) }

• 结果：

- 端口连接情况：

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

• h1 -- h4互通
• h2 -- h5互通
• h3 -- h6互通
• 其余主机不通

将h1，h2，h3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， 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h4，h5，h6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

3. 直接在Open vSwitch查看流表，提交OVS命令执行结果

• 查看流表

4. 提交主机连通性测试结果，验证流表的有效性

• 测试结果

5. 利用Wireshark抓包，分析验证特定报文

• 含有tag标签的报文（应该选择端口4，因为两个交换机之间才存在有tag的包）