MA-L, MA-M and MA-S: IEEE MAC Address Blocks Explained

Not every manufacturer needs millions of MAC addresses. To handle this, the IEEE allocates address space in three block sizes: MA-L, MA-M and MA-S.

MA-L (MAC Address Block Large)

A 24-bit OUI prefix (for example 00:1A:2B) that leaves 24 bits for the device — about 16.7 million addresses. This is the classic OUI most people think of, used by large vendors.

MA-M (MAC Address Block Medium)

A 28-bit prefix that gives a vendor roughly 1 million addresses. The prefix is longer than a standard OUI because the fourth byte is shared between vendors.

MA-S (MAC Address Block Small)

A 36-bit prefix providing about 4,096 addresses — ideal for small manufacturers or IoT startups.

Why it matters for lookups

Because MA-M and MA-S prefixes are longer, a correct lookup must match the longest registered prefix — exactly what our tool does. When you search a MAC, we show the block type so you know how the address space was allocated.

See it in action with our MAC lookup tool.