In this assignment, your task is to create a simple tree topology. You will assume each level i.e., core, aggregation, edge and host to be composed of a single layer of switches/hosts with a configurable fanout value (k) looks like:
代码：
# CustomTopo.py‘‘‘Coursera:- Software Defined Networking (SDN) course-- Module 3 Programming AssignmentProfessor: Nick FeamsterTeaching Assistant: Muhammad Shahbaz‘‘‘from mininet.topo import Topofrom mininet.net import Mininetfrom mininet.node import CPULimitedHostfrom mininet.link import TCLinkfrom mininet.util import irange,dumpNodeConnectionsfrom mininet.log import setLogLevelclass CustomTopo(Topo): ???"Simple Data Center Topology" ???"linkopts - (1:c1, 2:aggregation, 3: edge) parameters" ???"fanout - number of child switch per parent switch" ???def __init__(self, linkopts1, linkopts2, linkopts3, fanout=2, **opts): ???????# Initialize topology and default options ???????Topo.__init__(self, **opts) ???????????????????????????????# Add your logic here ... ???????self.fanout = fanout ???????core = self.addSwitch(‘c1‘) ???????for i in irange(1, fanout): ???????????aggregation = self.addSwitch(‘a%s‘ %i) ???????????self.addLink(core, aggregation, **linkopts1) ???????????for j in irange(1, fanout): ???????????????edge = self.addSwitch(‘e%s‘ %(fanout*(i-1)+j)) ???????????????self.addLink(aggregation, edge, **linkopts2) ???????????????for k in irange(1, fanout): ???????????????????host = self.addHost(‘h%s‘ %((fanout*(fanout*(i-1)+j-1))+k)) ???????????????????self.addLink(edge, host, **linkopts3) ??????????????????topos = { ‘custom‘: ( lambda: CustomTopo() ) }def simpleTest(): ???"Create and test a simple network" ???linkopts1 = dict(bw=10, delay=‘3ms‘, use_htb=True) ???linkopts2 = dict(bw=8, delay=‘4ms‘, loss=1, max_queue_size=900, ) ???linkopts3 = dict(bw=6, delay=‘5ms‘, loss=1, max_queue_size=800) ???topo = CustomTopo(linkopts1, linkopts2, linkopts3, fanout=2) ???net = Mininet(topo, host=CPULimitedHost, link=TCLink) ???net.start() ???print "Dumping host connections" ???dumpNodeConnections(net.hosts) ???print "Testing network connectivity" ???net.pingAll() ???net.stop()if __name__ == ‘__main__‘: ??# Tell mininet to print useful information ??setLogLevel(‘info‘) ??simpleTest()在mininet虚拟机上执行下面操作即可创建自定义的网络拓扑。函数simpleTest()创建网络并进行了简单的ping测试，从屏幕输出可以看到创建的过程。
mininet@mininet-vm:~/mininet$ sudo python CustomTopo.py
minnet sample
原文地址：http://www.cnblogs.com/soul-stone/p/7955562.html