What is a MAC address?
Why Interviewers Ask This
Interviewers use this question to quickly assess whether a candidate has the foundational knowledge required for Networking development. It reveals whether you understand the building blocks that more complex concepts rely on.
Answer
A MAC (Media Access Control) address is a unique hardware identifier assigned to a network interface card (NIC) by the manufacturer. It is a 48-bit (6-byte) address written in hexadecimal: 00:1A:2B:3C:4D:5E. The first 3 bytes (OUI) identify the manufacturer; the last 3 bytes are the device-specific identifier. MAC addresses operate at Layer 2 (Data Link) and are used for communication within a local network segment. Unlike IP addresses, MAC addresses are permanent (burned into hardware) and do not change when a device moves to a different network — though they can be spoofed in software. Switches use MAC address tables to forward frames to the correct port. ARP (Address Resolution Protocol) maps IP addresses to MAC addresses on a local network.
Pro Tip
If you're unsure about a detail, say so honestly and explain your reasoning. Interviewers respect candidates who can think through uncertainty rather than bluffing.