Mininet-WiFi car1-wlan0 Link Down in VirtualBox Environment

[Wang Rui Xing]

Dear Mr Ramon,

I ran this code on a native Ubuntu host and it worked perfectly. However, when I ran the exact same code inside a VirtualBox virtual machine, the car1-wlan0 link failed to come UP (it remains in a DOWN/NO-CARRIER state)." I have already tested it using the points mentioned below but the error is existing. Can you please give me idea or solution the problem?

Best Regards,

Aung Aung

• Range & Propagation: Increased AP/Station range to 150m and moved the propagation model declaration before net.build().

• Manual Interface Control: Used ip link set up and ifconfig commands both in the script and CLI to force the interface "UP."

• Manual Association: Attempted to force connection using iw dev connect and iwconfig essid commands.

• WPA Supplicant: Created a custom /tmp/car1.conf and ran the wpa_supplicant daemon in the background.

• Wmediumd & Interference: Disabled wmediumd and interference mode to reduce CPU overhead and driver instability.

• Controller Isolation: Tested with both simple_switch_13 and a custom Blockchain controller to check for Packet-In messages.

• Virtualization Settings: Set VirtualBox acceleration to KVM and disabled the Ubuntu network-manager service.

• Topology Logic: Used ac_method='manual' and net.addLink(car1, ap1) to treat the wireless link as a static software bridge.

Error ------------------

mininet-wifi> car1 ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
162: car1-wlan0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
    link/ether 00:00:00:00:00:33 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.3/24 brd 10.0.0.255 scope global car1-wlan0
       valid_lft forever preferred_lft forever
    inet6 2001::1/64 scope global tentative
       valid_lft forever preferred_lft forever
mininet-wifi> car1 iw dev car1-wlan0 link
Not connected.

================================================================

That is my mininet-wifi python code file.

#!/usr/bin/env python3

import sys
from mininet.log import setLogLevel, info
from mininet.node import RemoteController, OVSSwitch
from mn_wifi.net import Mininet_wifi
from mn_wifi.link import wmediumd
from mn_wifi.cli import CLI
from mn_wifi.wmediumdConnector import interference


def topology(args):

    info("*** Creating Mininet-WiFi network\n")
    net = Mininet_wifi(
        controller=RemoteController,
        switch=OVSSwitch,
        link=wmediumd,
        wmediumd_mode=interference
    )

    info("*** Creating nodes\n")

    # OpenFlow Switch
    s1 = net.addSwitch(
        's1',
        cls=OVSSwitch,
        protocols='OpenFlow13',
        position='200,100,0'
    )

    server = net.addHost('server', ip='10.0.0.1/24', position='200,150,0')

    # Access Points (NO WPA – blockchain handles auth)
    ap1 = net.addAccessPoint(
        'ap1',
        ssid='ssid-ap1',
        mode='g',
        channel='1',
        range=100,
        position='100,50,0'
    )

    ap2 = net.addAccessPoint(
        'ap2',
        ssid='ssid-ap2',
        mode='g',
        channel='6',
        range=100,
        position='300,50,0'
    )

    # Mobile Node (Vehicle)
    car1 = net.addStation(
        'car1',
        mac='00:00:00:00:00:33',
        ip='10.0.0.3/24',
        range=30,
        position='10,50,0'
    )

    # Ryu Controller (OpenFlow 1.3 default port)
    ryu = net.addController(
        'ryu',
        controller=RemoteController,
        ip='127.0.0.1',
        port=6653
    )

    info("*** Configuring nodes\n")
    net.configureNodes()

    info("*** Creating links\n")
    net.addLink(ap1, s1)
    net.addLink(ap2, s1)
    net.addLink(s1, server)


    info("*** Setting propagation model\n")
    net.setPropagationModel(model='logDistance', exp=4.5)

    if '-p' not in args:
        net.plotGraph(min_x=-50, min_y=-50, max_x=500, max_y=150)

    info("*** Configuring mobility\n")
    net.startMobility(time=0)

    net.mobility(
        car1,
        'start',
        time=30,
        position='10,50,0'
    )

    net.mobility(
        car1,
        'stop',
        time=90,
        position='400,50,0'
    )

    net.stopMobility(time=91)

    info("*** Starting network\n")
    net.build()
    ryu.start()
    ap1.start([ryu])
    ap2.start([ryu])
    s1.start([ryu])


    info("*** Running CLI\n")
    CLI(net)

    info("*** Stopping network\n")
    net.stop()


if __name__ == '__main__':
    setLogLevel('info')
    topology(sys.argv)

[Ramon Fontes]

Hi Aung Aung,

You may want to run the code with debug logging enabled to better
understand what is going wrong. At first glance, the issue may be
related to a missing package or the generic kernel version used by the
VM.

--
Ramon Fontes

Em seg., 2 de fev. de 2026 às 05:56, Wang Rui Xing
<aungsanli...@gmail.com> escreveu:

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[Wang Rui Xing]

Dear Mr Ramon,

Thank you, sir! I forgot to check the debug logs earlier. I found the main issue was 'bash: hostapd: command not found.' After installing the package, the issue was completely resolved. It's working perfectly now.

Best Regards,

Aung Aung