Which device property is used to uniquely identify network-connected devices?

• A. IP address
• B. MAC address
• C. Hostname
• D. Subnet mask

Answer: (B)

MAC addresses are the unique hardware identifiers assigned to each network interface card. They live at the data link layer and are used by the local network to deliver frames to the correct device, with ARP helping map an IP address to its corresponding MAC on the same LAN. Unlike IP addresses, which can change, be reused, or be assigned differently on different networks, a NIC’s MAC address is designed to be globally unique and tied to that hardware. Hostnames are just human labels we assign and can be changed or duplicated across machines, while subnet masks describe the network portion of an IP address rather than identifying a device. Therefore, the MAC address is the property that uniquely identifies network-connected devices on a local network.