So I know the first 24 bits of a MAC address are assigned to the manufacturer and the last 24 bits are assigned directly the to device. So that means there are 16,777,216 unique blocks of addresses for the manufacturer to use and 16,777,216 addresses per block.
In the grand scheme of things though, that seems like a small amount of addresses. Like I doubt there are 16 million companies manufacturing network adapters, but I imagine a lot of these companies have to register multiple blocks as they have sold more than 16 million units. Like Nintendo for instance would need around 9 blocks just for the amount of Switches sold, and that doesnât include all the GameCube LAN adapters, DSs, Wiis, 3DSâs and Wii Uâs they sold. So why donât they have an IPv6-like 128-bit MAC address instead?
Comments
wrosecrans ⢠27 points â˘
Basically because Ethernet originally dates back to the 1970âs, and early versions didnât even support routing to interconnect Ethernets. The idea that it would eventually grow to be used on a global network with millions of connected devices where you could plausibly have issue with MAC address collisions wasnât in the scope of the original design, and would have seemed silly in an age before common personal computers. Then, backwards compatibility.
track me
Poddster ⢠9 points â˘
Just to clarify /Â emphasise something youâve said: Mac addresses were originally intended for devices/adapters on an local ethernet-based network.
The fact they should became used as a generic ânetwork machine idâ across the internet is because of laziness, and people using what they had available.
The other standards like Bluetooth started to use them instead of making their own scheme.
[deleted] ⢠11 points â˘
48-bit is a huge space - about 30000 addresses for each person on a planet
That would be true if the full address space were available. However, the first 24 bits are usually used for the manufacturer code, leaving only 224 for a device ID. Manufacturers do exhaust the 17-million addresses in their address space and re-use them - often shipping devices with duplicate MACs in different countries where theyâre unlikely to ever end up on the same LAN.
nuclear_splines ⢠4 points â˘
48-bit is a huge space - about 30000 addresses for each person on a planet
That would be true if the full address space were available. However, the first 24 bits are usually used for the manufacturer code, leaving only 224 for a device ID. Manufacturers do exhaust the 17-million addresses in their address space and re-use them - often shipping devices with duplicate MACs in different countries where theyâre unlikely to ever end up on the same LAN.
tcpukl ⢠1 points â˘
Can a manufacturer get a second code? Not sure why not.
ukezi ⢠2 points â˘
They can and they do. TI for instance has currently 351 prefixes.
[deleted] ⢠1 points â˘
Yes manufacturers can get additional codes, and yet, duplicate MAC assignments are documented, so they donât all go to the trouble.
nuclear_splines ⢠1 points â˘
Yes manufacturers can get additional codes, and yet, duplicate MAC assignments are documented, so they donât all go to the trouble.
htl5618 ⢠6 points â˘
Not sure what the problem is, MAC is used for identifying in a local network only, and the last 24 bits can be randomized. There are not many networks with 16 million devices connected to the same switch.
Fazaman ⢠4 points â˘
There are not many networks with 16 million devices connected to the same switch.
True, but youâd need many many less than that to almost guarantee a collision. Birthday paradox and all that.
That said, youâd have to have many devices all from the same manufacturer and probably would need some very old ones to mix in with some new ones, because the theyâre likely to have not reused mac addresses on timescales that would cause two devices to be vaguely useful in the same network together, but ⌠well ⌠you get the idea.
BornConcentrate5571 ⢠2 points â˘
Birthday paradox does not apply to a scenario where ID values are not assigned randomly. Manufacturers record the MAC addresses they use, so any collisions would be entirely intentional.
Fazaman ⢠1 points â˘
Good point.
[deleted] ⢠2 points â˘
That makes sense. I guess the chance of 2 devices with the same MAC connecting to the same network are incredibly unlikely.
htl5618 ⢠3 points â˘
also MAC can be randomized for each different network you join, which is the default now.
-1_0 ⢠1 points â˘
https://networkengineering.stackexchange.com/questions/23566/what-are-eui-48-and-eui-64
wjrasmussen ⢠1 points â˘
Hey, why didnât the Wright brothers start with making jet airplanes? Those guys were dolts.
[deleted] ⢠1 points â˘
A lot of standards we use now, which no longer make sense, where invented 40 or 50 years ago, when they did make sense.