Exception Error in mininet

Question

I have used Mininet to create a simple custom topology. It worked correctly When I was running it for the first time, but after that I received following error message:

Exception: Error creating interface pair (s1-eth1,h1-eth0): RTNETLINK answers: File exists

what is it and how can I solve it?

here is my topology:

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


class CustomTopo (Topo):

    def build(self):

        S1 = self.addSwitch('s1')

        H1 = self.addHost('h1')
        H2 = self.addHost('h2')

        self.addLink(S1, H1)
        self.addLink(S1, H2)


topo = CustomTopo()
net = Mininet(topo)
net.start()

topos = {'mytopo': CustomTopo}

and for more information I use Mininet 2.3.0d1

I run it by following command without remote controller and received another error: sudo mn --custom /home/bob/Desktop/Mtopo.py --topo=mytopo --mac

the error is: Exception: Please shut down the controller which is running on port 6653

I checked netstat -nl | grep 6653 but there is no active session on port 6653 and there is no other controller to shutdown.

The code is fine (I had no problem running it). Do you run the code with sudo (as root) ? — Daniel, Jun 01 '18 at 18:15
@Daniel yes I run it as root with : **sudo mn --custom /home/bob/Desktop/Mtopo.py --topo=mytopo --mac --controller=remote** I totally get confused and do not know what I have to do. — Babak Memar, Jun 06 '18 at 13:22
@Daniel I found out that my topology create each host twice, so it can not add link between s1 and h1 for the second time. What do I have to do to solve it? — Babak Memar, Jun 10 '18 at 07:31

score 0 · Answer 1 · answered May 29 '18 at 06:28

0

use this library:

from mininet.link import TCLink, Intf

and this when you add a link:

self.addLink(s1, h1, cls=TCLink)

answered May 29 '18 at 06:28

dside

98
7

Unfortunately the error still remains, I also use 'sudo mn -c' but nothing happen. – Babak Memar May 30 '18 at 09:06
can you provide more details about using the script and the topo? – dside May 31 '18 at 10:01
Sure, you can see the script in main question and I saved it as Mtopo.py in desktop. To run it I use following command: **sudo mn --custom /home/bob/Desktop/Mtopo.py --topo=mytopo --mac** if you want more details, let me know what those are. @dside – Babak Memar May 31 '18 at 12:05

Daniel · Accepted Answer · 2018-06-12T14:21:03.493

You actually start Mininet twice. Once in your script and the other with the command line. Either change your script to:

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

class CustomTopo (Topo):

    def build(self):

        S1 = self.addSwitch('s1')

        H1 = self.addHost('h1')
        H2 = self.addHost('h2')

        self.addLink(S1, H1)
        self.addLink(S1, H2)


topo = CustomTopo()
net = Mininet(topo, controller=lambda name: RemoteController(name, ip='127.0.0.1', protocol='tcp', port = 6633), autoSetMacs=True)
net.start()
CLI(net)
net.stop()

save to start_topology.py and run as

sudo python start_topology.run

or change your script to

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


class CustomTopo (Topo):

    def build(self):

        S1 = self.addSwitch('s1')

        H1 = self.addHost('h1')
        H2 = self.addHost('h2')

        self.addLink(S1, H1)
        self.addLink(S1, H2)


topo = CustomTopo()
topos = {'mytopo': CustomTopo}

save to mytopo.py and run as

sudo mn --custom mytopo.py --topo=mytopo --mac --controller=remote,ip=127.0.0.1,port=6633

(change the IP and PORT for your controller accordingly)

Your answer is complete, thanks. I chose your first solution, just one question, in this case how can I assign MAC address to hosts? I mean exactly like when I use **sudo mn --mac**, I do not want random MAC address. — Babak Memar, Jun 12 '18 at 12:57
You should add the parameter autoSetMacs=True to the Mininet constructor. I have edited my answer to include this. — Daniel, Jun 12 '18 at 14:22
So I can use all parameters [http://mininet.org/api/classmininet_1_1net_1_1Mininet.html#a2b42ae2e15dceca476abf8ed9573834c] in constructor. Thanks a lot @Daniel — Babak Memar, Jun 13 '18 at 07:41

Exception Error in mininet

2 Answers2