实验1：SDN拓扑实践

（一）基本要求

1、使用Mininet可视化工具，生成下图所示的拓扑，并保存拓扑文件名为学号.py。

2、使用Mininet的命令行生成如下拓扑：

(a)3台交换机，每个交换机连接1台主机，3台交换机连接成一条线。

(b)3台主机，每个主机都连接到同1台交换机上。

在2 (b)的基础上，在Mininet交互界面上新增1台主机并且连接到交换机上，再测试新拓扑的连通性。

3. 修改过的“学号.py”代码、Mininet运行结果

（二）进阶要求

点击查看代码

#!/usr/bin/python
from curses.panel import top_panel
from mininet.topo import Topo


class MyTopo(Topo):
     	
        def build(self):
               
                L1 = 2
                L2 = L1 * 2 
                L3 = L2 * 2
                c = []
                a = []
                e = []
                
                # add core ovs  
                for i in range( L1 ):
                        sw = self.addSwitch( 'c{}'.format( i + 1 ) )
                        c.append( sw )
        
                # add aggregation ovs
                for i in range( L2 ):
                        sw = self.addSwitch( 'a{}'.format( L1 + i + 1 ) )
                        a.append( sw )
        
                # add edge ovs
                for i in range( L3 ):
                        sw = self.addSwitch( 'e{}'.format( L1 + L2 + i + 1 ) )
                        e.append( sw )
        
                # add links between core and aggregation ovs
                for i in range( L1 ):
                        sw1 = c[int(i)]
                        for sw2 in a[int(i/2)::int(L1/2)]:
                        # self.addLink(sw2, sw1, bw=10, delay='5ms', loss=10, max_queue_size=1000, use_htb=True)
                                        self.addLink( sw2, sw1 )
        
                # add links between aggregation and edge ovs
                for i in range( 0, int(L2), 2 ):
                        for sw1 in a[int(i):int(i+2)]:
                                for sw2 in e[i:i+2]:
                                        self.addLink( sw2, sw1 )
        
                #add hosts and its links with edge ovs
                count = 1
                for sw1 in e:
                        for i in range(2):
                                host = self.addHost( 'h{}'.format( count ) )
                                self.addLink( sw1, host )
                                count += 1
topos = { 'mytopo': ( lambda: MyTopo() ) }