Reserved MAC-addresses (some are assigned anyway?)

Question

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 1

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.

Answer 2

The following OUI are reserved as per RFC 5342:

1. OUI 01:00:5E:(00:00:00-7f:ff:ff) - Used for IPV4 Multicast and MLPS Multicast.

2. OUI 00:00:5E:(00:01:00 – 00:01:FF) - Used for Virtual Router Redundancy Protocol (VRRP) IPV4

3. OUI 00:00:5E:(00:02:00 – 00:02:FF) - Used for Virtual Router Redundancy Protocol (VRRP) IPV6

4. OUI 33:33:00 – 33:33:FF - Reserved for IPV6 Multicast

5. OUI CF:00:00 – CF:FF:FF - Reserved by IANA for PPP(Point to Point Protocol)

6. OUI 00:00:5E (00:00:00 - 00:00:FF) - Requires IESG Ratification for allocation.

Answer 3

Was looking into this myself.. I know it's been a while since the post was active.. but I found these to be ok to use locally:

• x2-xx-xx-xx-xx-xx
• x6-xx-xx-xx-xx-xx
• xA-xx-xx-xx-xx-xx
• xE-xx-xx-xx-xx-xx

Source: https://honeywellaidc.force.com/supportppr/s/article/Locally-Administered-MAC-addresses

Answer 4

The registration authority for MAC addresses is the IEEE. It hands out OUIs (Organizationally Unique Identifiers), which give you a three byte prefix, and 2^24 addresses within it, for a fee (currently 2 995USD). You also get the rights to the corresponding multicasts, which have the prefix with the lowest bit of the first byte set. For instance, 00:80:C2 is allocated to the IEEE 802.1 committee, which uses 01:08:C2:00:00:00 for Spanning tree.

So, there isn't really a list of reserved addresses. There is a list of OUIs that have been allocated, unless the buyer has paid (a lot) extra for privacy. You can use any address that has the local bit set freely. A tiny fraction of multicast addresses have a significant meaning because heavyweights like IEEE, Cisco, IANA assign meanings to them. From the IEEE registration point of view, there is no particular significance to these blocks (except possibly to those it has allocated to itself).

Now, how did the 01-00-5E range end up allocated to the Information Sciences Institute? The simple answer is that they paid for it. So, really the question should be 'how did the Internet get to use part of the range allocated to ISI?'. The answer is that the IANA used to be run from an office in ISI: specifically IANA was the legendary Jon Postel

Bottom line: you are on a bit of a fool's errand. You can distinguish local addresses and multicast addresses, and make some attempt to tie up allocated unicast addresses to vendor blocks. And you can probably do a bit more with well-known multicast addresses but only by tracking down individudal vendor's documentation (IANA is obviously an important one but only definitive for 1 of the 2^22 available blocks). One of the best places to start is probably the Wireshark codebase.