CODEWITHSUNDEEP
pythonmininettopology
helen
helen

Reputation: 587

Creating a topology using python

I want to build a mininet topology using python API. My topology is supposed to have 2 controllers, 3 switches and each switch will have several hosts connected to it (number of connected hosts is 2, 4, 1 respectively). Here is the code:

#!/usr/bin/python                                                                                                                                                                   

import time
from mininet.net import Mininet
from mininet.node import Controller, OVSKernelSwitch, RemoteController
from mininet.cli import CLI
from mininet.log import setLogLevel, info


def net():

    net = Mininet(controller=RemoteController, switch=OVSKernelSwitch)
    c1 = net.addController('c1', controller=RemoteController, ip="127.0.0.1", port=6653)
    c2 = net.addController('c2', controller=RemoteController, ip="127.0.0.1", port=7753)

    s_n = 3 #number of switches
    c_n = 2 #number of controllers
    hosts = []
    amount = [2, 4, 1] # number of hosts that each switch has

    info( "*** Creating switches\n" )
    switches = [ net.addSwitch( 's%s' % s ) for s in range( 1, s_n ) ]

    index1 = 0 
    L_in = 0
    index2 = 0

    info( "*** Creating hosts\n" )
    for s in switches:
        L_in = (L_in + 1)
        if L_in <= len(amount):

            index1 = (index2 + 1)
            index2 = (index1 + amount[L_in]) - 1
            hosts = [ net.addHost( 'h%s' % n ) for n in ( index1, index2 ) ]
            for h in hosts:
                net.addLink( s, h )
        else:
            break

    # Wire up switches
    last = None
    for switch in switches:
        if last:
            net.addLink( last, switch )
        last = switch

    net.build()
    c1.start()
    c2.start()

    for sw in switches[:c_n]:
        sw.start( [c1] )

    for sw in switches[c_n:]:   
        sw.start( [c2] )

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


if __name__ == '__main__':
    setLogLevel( 'info' )
    net()

But when I run the code, it is not working correctly. For example, I expect 3 switches, but 2 switches are created. I expect 7 hosts, but 4 hosts are created. The connection between hosts and switches is not correct, too. Here is the output:

*** Creating switches
*** Creating hosts
*** Configuring hosts
h1 h4 h5 h5 
*** Starting controller
c1 c2 
*** Starting 2 switches
s1 s2 ...
*** Starting CLI:
mininet> net
h1 h1-eth0:s1-eth1
h4 h4-eth0:s1-eth2
h5 h5-eth0:s2-eth2
h5 h5-eth0:s2-eth2
s1 lo:  s1-eth1:h1-eth0 s1-eth2:h4-eth0 s1-eth3:s2-eth3
s2 lo:  s2-eth1:h5-eth0 s2-eth2:h5-eth0 s2-eth3:s1-eth3
c1
c2

Upvotes: 0

Views: 2901

Answers (1)

9000
9000

Reputation: 40894

A number of problems here.

range(1, n) produces numbers from 1 no n-1, not to n.

You define function net that will shadow the previous (imported?) definition of module net. Call it make_net or something.

Explicit loop indices like L_in is almost always a bad idea, same as non-descriptive names as index2.

Something like this should give you the idea:

n_switches = 3
hosts_per_switch = [2, 4, 1]

switches = [addSwitch("s%d" % n + 1) for n in range(n_switches)]

for (switch, number_of_hosts) in zip(switches, hosts_per_switch):  # Pair them.
    hosts = [addHost("h%d" % n + 1) for n in range(number_of_hosts)]
    for host in hosts:
        addLink(switch, host)

Upvotes: 1

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