this post was submitted on 21 Feb 2026
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Tell Me everything you want about MAC addresses
Is this a kink?
The first six hexadecimal digits of the Mac address are referred to as the oui, or organizationally unique identifier. They are supposed to all be registered, but with modern systems, mac address randomization is common, so the Mac address in use can be little better than nonsense.
I have a theory that some of the more budget oriented manufacturers (think Ali express), just don't bother using a registered mac address at all.
This all makes my job harder as a network admin, I usually need to look up what a device is by mac address to help identify what it is and what it's doing. I need to make sure everything is on the right network, and I can't do that if I don't know what anything is.
The last six hexadecimal digits of the Mac are simply to uniquely identify the interface that the Mac is burned into. This also means that any systems with multiple network ports, have different mac address on each port. Some things are exempt, like network switches, but for the most part, every interface has, or is supposed to have, a unique mac address.
Also, the mac isn't hex, it's binary. Hex is just how we've decided to present it to users. The switches, routers, and interfaces don't work with the hex, only the binary. Same for IP addresses, which normal are shown in "dotted decimal notation", but are just binary. But you didn't ask about IP.
Did you need me to whisper ouis into your ear and you can guess what company is registered to that oui?
Fun fact, when I worked for Alstom and programmed their electric substations, they had a 10bit network and proprietary network cards, and the prototypes sometimes had the same MAC address 😁😅
Nothing sexier than someone who knows what they're talking about.
Sorry, I'm married.
:p
My wife doesn't think it's sexy, she usually just falls asleep whenever I get into a topic I'm passionate about. Oh well.
So if you plug the same device into a different network using the same port, it's the same MAC?
The device mac doesn't change unless mac randomization is on.
I hate that, as far as I know, on Android you can't choose the "randomized" MAC
You want to pick your own MAC? At least you can set it to not be random for a specific network.
Yes, by picking my own MAC as with my linux laptop I could share pre approved network access on both devices (although not at the same time)
And that is exactly why it's not allowed.
The MAC, at least as it was conceptualised (as they said, MAC randomisation etc. mess with this), is a unique identifier for that specific device. It doesn't change, and only one device has that specific MAC.
Or more specifically, that specific network adaptor, the hardware responsible for connecting to networks. So one computer might have multiple MACs if, for example, it has an Ethernet port and a wifi card.