Find the vendor name of a device by entering an OUI or a MAC address
What are CID and IAB assignments?
They are two different assignments, and neither behaves like an ordinary vendor prefix. A CID, Company ID, is a 24-bit identifier that cannot be used to generate globally unique MAC addresses, because the addresses derived from it are locally administered. An IAB, Individual Address Block, was a small 24-bit block the IEEE stopped issuing on 1 January 2014 and replaced with MA-S.
CID: a 24-bit identifier that cannot make a unique MAC address
A CID has the same length as an OUI and looks the same in the registry, but the two are not interchangeable. The IEEE states that a CID is not used to create globally unique EUI-48 or EUI-64 identifiers. Addresses an organization derives from its CID have the U/L bit set, which marks them as locally administered: they belong to no globally administered block, and a lookup that tests the address against registration data finds no registrant for the interface itself.
That is why a CID is the wrong answer to "I need a range of addresses my devices can present worldwide". It is the right answer when an organization needs a company identifier for purposes other than manufacturing network interfaces.
IAB: the small block that MA-S replaced
An IAB was a block of 4,096 EUI-48 addresses, issued to organizations that needed far fewer addresses than the 16,777,216 of an MA-L. The IEEE retired the scheme on 1 January 2014 and points new applicants to MA-S, which also provides 4,096 EUI-48 addresses. The block sizes sets out the three current lengths.
Why a lookup still answers for them
An IAB issued before 2014 is still a real assignment, and the interfaces built from it are
still in use, so the registration data is kept and the lookup resolves those prefixes. A CID
is likewise a real registration. In both cases the answer names the organization the
identifier was assigned to, and the blockType field of an API response says which
kind of assignment matched — the API documentation lists the values.
What neither gives you is a globally administered prefix from which unique MAC addresses can be minted. A device presenting an address derived from a CID is locally administered, and a lookup reports that as no vendor found unless the address happens to fall inside a registered block.
Look one up
Paste a prefix into the MAC address lookup to see which assignment type it matches and which organization holds it.
Related questions
Sources and review
Last reviewed: . Technical claims on this page follow the primary sources below; operating-system interfaces change between releases, so check them against your own device version.