Which OSI layer is associated with MAC addresses such as EUI-48 and EUI-64, and is where switches operate?

• A. Transport layer
• B. Network layer
• C. Data Link layer
• D. Physical layer

Answer: (C)

MAC addresses like EUI-48 and EUI-64 identify network interface hardware on a local link, and the duties that revolve around addressing and framing on that local link belong to the Data Link layer. Switches operate at this layer, learning which devices live on which ports by seeing the source MACs and then forwarding frames to the correct destination MAC through the appropriate port. The Data Link layer includes the MAC sublayer, which handles addressing and access to the physical medium.

Other layers don’t fit this context: the Network layer uses IP addresses and routing, the Transport layer uses ports for end-to-end delivery, and the Physical layer handles raw electrical signals rather than addressing or switching.