What does a zero MAC address refer to?

Question

I have the Ubuntu 16.04 system running on an ASUS Zenbook. When I run the following code to write out the MAC addresses of all my interfaces:

#include <QCoreApplication>
#include <QNetworkInterface>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    auto interfaces = QNetworkInterface::allInterfaces();
    for (const auto& i : interfaces)
        qDebug() << i.humanReadableName() << "; "<< i.hardwareAddress() << '\n';

    return a.exec();
}

I get:

"lo" ; "00:00:00:00:00:00"

"wlp2s0" ; "00:21:5C:B2:C7:58"

My laptop has a built in WiFi and there is no Ethernet cable port.

I am really wondering what does this zero MAC address refer to.

So far my research turned me to forums where this was either a problem with the drivers, or with the Kaspersky antivirus.

Is there any legitimate meaning of this MAC address, or is it an error?

MAC addresses are layer-2 addresses used by some layer-2 protocols, specifically, the IEEE 802 LAN protocols, e.g. ethernet (IEEE 802.3), Wi-Fi (IEEE 802.11), token ring (IEEE 802.5), etc. Your loopback interface doesn't use one of these layer-2 protocols, so it really has no MAC address. Some layer-2 protocols that do use MAC addresses use 48-bit MAC addresses, and some use 64-bit MAC addresses. Many WAN protocols, e.g. PPP, HDLC, Frame Relay, ATM, etc, do not use MAC addresses. — Ron Maupin

negacao negacao · Accepted Answer · 2016-12-24T20:51:10

localhost, the loop back interface. It's legitimate. There is a good explanation of what this is on Wikipedia: https://en.wikipedia.org/wiki/Localhost

What does a zero MAC address refer to?

1 Answers