最近在做静态路由转发实验（计算机网络课程实验），实验课程给出了一定的代码，不过老师在实验上挖了一些坑需要我们填补。

先贴出实验代码：

#!/usr/bin/python

from mininet.topo import Topo
from mininet.net import Mininet
from mininet.cli import CLI

class RouterTopo(Topo):
    def build(self):
        h1 = self.addHost('h1')
        h2 = self.addHost('h2')
        h3 = self.addHost('h3')
        r1 = self.addHost('r1')

        self.addLink(h1, r1)
        self.addLink(h2, r1)
        self.addLink(h3, r1)

if __name__ == '__main__':
    topo = RouterTopo()
    net = Mininet(topo = topo, controller = None) 

    h1, h2, h3, r1 = net.get('h1', 'h2', 'h3', 'r1')
    h1.cmd('ifconfig h1-eth0 10.0.1.11/24')
    h2.cmd('ifconfig h2-eth0 10.0.2.22/24')
    h3.cmd('ifconfig h3-eth0 10.0.3.33/24')

    h1.cmd('route add default gw 10.0.1.1')
    h2.cmd('route add default gw 10.0.2.1')
    h3.cmd('route add default gw 10.0.3.1')

    for h in (h1, h2, h3):
        h.cmd('./scripts/disable_offloading.sh')
        h.cmd('./scripts/disable_ipv6.sh')

    r1.cmd('ifconfig r1-eth0 10.0.1.1/24')
    r1.cmd('ifconfig r1-eth1 10.0.2.1/24')
    r1.cmd('ifconfig r1-eth2 10.0.3.1/24')

    r1.cmd('./scripts/disable_arp.sh')
    r1.cmd('./scripts/disable_icmp.sh')
    r1.cmd('./scripts/disable_ip_forward.sh')

    net.start()
    CLI(net)
    net.stop()

在Ubuntu下运行该router_topo.py程序时，使用命令sudo mn --custom router_topo.py --topo router 出现了invalid topo name错误。截图如下：

后面查看stackflow后解决了该问题。

在class RouterTopo定义前添加一行TOPOS = {'router':(lambda:RouterTopo())}

这样就可以解决了，注意不要缩进。成功截图如下：