Reserved MAC-addresses (some are assigned anyway?)

networking ethernet mac-address
user1793963 picture user1793963 · Feb 5, 2013 · Viewed 14.7k times · Source

I'm trying to make a list of all MAC addresses that are reserved, do not exist, should not be used, should only be used locally etc. (Just like the list of reserved IP-addresses on Wikipedia, but for MAC.) Basically I want to loop over all MAC-addresses from a switch and filter out the "real" ones.

This page suggests all addresses starting with 00-00-5E or 01-00-5E are reserved, but when I look them up it seems like 00-00-5E is also assigned to the Information Sciences Institute (part of a university in California).

So 2 questions:

1) Is there any place I can find a list of reserved MAC-adresses?

2) What's up with 00-00-5E? Is only part of that range reserved, or is there some reason they assigned it to ISI?

Answer

James Ethridge picture James Ethridge · May 1, 2013

I was just looking into this myself recently. I believe that the IANA (which you refer to in one of your links) will give the most authoritative answer: IANA Ethernet Number Assignments

I don't think that this means that these addresses can never be used though. According to RFC5342, Section 2.1

"The 2**8 unicast identifiers from 00-00-5E-00-00-00 through 00-00-5E-00-00-FF are reserved and require IESG Ratification for allocation (see Section 5.1)."

So basically, it appears you need special permission from IESG (Internet Engineering Steering Group) to get an address in that range, which I suppose the ISI has obtained somehow.

Section 2.1 of RFC5342 deals with 48-Bit MAC Identifiers and OUIs, and it doesn't make any mention of any address ranges that are strictly forbidden or permanently reserved from what I've understood.

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