IANA Multicast Mapping Thoughts

mistabrumley89

Can someone explain the logic to me of why they decided to use 25 bits for the 01:00:5E:XX:XX:XX address instead of the first 24 bits? Why is the 25th bit turned off? I was just curious because it has been poking at my brain for a couple of days.

EdTheLad

Back in the early 1990s, Steve Deering was bringing some of his research work on IP multicasting to fruition, and he wanted the IEEE to assign 16
consecutive Organizational Unique Identifiers (OUIs) for use as IP multicast MACaddresses. Because one OUI contains 24 bits worth of address space, 16 consecutive OUI’s would supply a full 28 bits worth of MAC address space and would permit a one-to-one mapping of Layer 3 IP multicast addresses to MAC addresses. Unfortunately, the going price for an OUI at the time was $1000 and Steve’s manager, the late Jon Postel, was unable to justify the $16,000 necessary to purchase the full 28 bits worth of MAC addresses.
Instead, Jon was willing to spend $1000 to purchase one OUI out of his budget and give half of the addresses (23 bits worth) to Steve for use in his IP multicast research.

mistabrumley89

Someone give this man a tall glass of ice cold milk, and a plate of homemade cookies!