In simplest terms, a MAC address is a 12-digit string typically written in six hexadecimal pairings separated by a colon or a hyphen, for the purpose of identifying network participants. The MAC protocol is how your router or gateway can tell your PC from your iPhone, and the reason why LANs are way better at correctly identifying mail recipients than your local postal service.
As with any other fundamental element of modern networking, MAC addresses are a doorway into copious layers of telecom knowledge – all relevant to how they operate. Not to worry, though: our goal here isn’t to intimidate, but offer a no-nonsense introduction to the topic for anyone curious enough to be reading these lines.
And here’s an idea toward that end: let us, for now, move on to some less abstract facts about MAC addresses before expanding on their specifications and how they work. After all, most netizens will already be familiar with quite a few of their use cases. But it’s safe to say that anyone whose knowledge of interfacing tech is strong enough for them to grasp a colorless list of protocol specifications probably doesn’t need to have MAC addresses explained to them in the first place.
Where are MAC addresses used the most?
The very meaning behind the initialism – which stands for “media access control” – already brings us to one of the earliest notable roles that MAC addresses had in modern communications. Because even the influential Open Systems Interconnection model, as eccentrically unique as it was, still relied on MAC addresses as part of every infrastructural proposal in the late ’80s and early ’90s.
It always bears repeating that despite losing the protocol wars to TCP/IP, the OSI model massively influenced the very fabric of networking. This is why it’s still widely used as a teaching material across virtually every IT discipline. And one of the many moving parts in this curious framework happened to be a sublayer of the ISO data link layer dedicated to the MAC protocol.
Moving away from history books, MAC addresses also proved worthy of a roster spot in the TCP/IP suite. And so to this date, the underlying World Wide Web tech uses them in combination with similar-purposed IP addresses in order to do its interconnectivity magic.
If we return to our clunky definition of MAC addresses from the opening paragraph, we can actually narrow them down to something called Extended Unique Identifiers separated by two numbering spaces. The Institute of Electrical and Electronics Engineers manages this specification, and so, every device on one of its IEEE 802 networks is assigned a EUI-48 address. The number itself is a reference to the 48-bit address space every such designation contains.
Either way, Wi-Fi (802.11) networks are one of the largest dependents on MAC addresses nowadays. Though they are equally viable for Ethernet connectivity and have also been included in every Bluetooth specification to date.
While this technology has been around for a long time, its practicality already prompted the development of a newer specification called EUI-64. Like the moniker implies, these pointers use 64 bits of address space and form the foundation for IPv6 addresses. Those extra supported data carrier units are also the main reason we won’t be running out of IPv6 addresses anytime soon.
The IPv6 specification has so far seen a multitude of pretty niche use cases, as well. Those include protocols in the vein of IEEE 1394, ZigBee, 802.15.4, and 6LoWPAN.
UAA vs LAA MAC addresses
Another popular classification of MAC addresses is the so-called UAA-LAA division. This one is way easier to grasp than using bit width, as it revolves solely around their level of application. More specifically, these abbreviations stand for Universally and Locally Administered Addresses, respectively.
UAA designations are given by hardware manufacturers, whereas LAA addresses are assigned at the discretion of network administrators. Note that this doesn’t even mean that LAA MAC addresses cannot be unique, given the sheer range of their address space.
Is a MAC address anonymous?
Believe it or not, the answer to this isn’t a resounding “no”. Of course that this sort of a labeling system can’t offer much in the way of anonymity as it wasn’t designed to do so, but modern IT applications have gotten so clever that the chances of having one’s MAC address tracked online are minuscule. Most contemporary practices devised for that purpose revolve around MAC address anonymization techniques which use a one-way hashing algorithm to obfuscate any physical identifiers.
Such solutions are primarily meant to protect you on public WiFi networks, however. So don’t think they’ll do much of anything under the scrutiny of a resourceful sysadmin. That aside, MAC addresses are only used for communication between your device and the first serviceable router standing between them and the web. Meaning that even without a VPN, you aren’t broadcasting your physical device identifier online, disregarding some freakishly unlikely cybersecurity gaffes.