Which term refers to the unique identifier assigned to a network interface?

The term that refers to the unique identifier assigned to a network interface is the MAC address. A MAC (Media Access Control) address is a hardware identifier that is embedded into a network interface card (NIC) by the manufacturer. Each MAC address is unique to the device, ensuring that no two devices on the same network can have the same MAC address, which helps facilitate direct communication between devices within a local area network (LAN).

Unlike an IP address, which can change based on the network configuration, the MAC address remains constant for the device across different networks. It operates at the data link layer of the OSI model, playing a crucial role in network protocols such as Ethernet. In contrast, the other terms listed have different purposes: an Ethernet ID is not a standardized term widely recognized in networking; a host name is a human-readable label assigned to a device on a network, which can correspond to an IP address but does not serve as a unique identifier for the device's network interface; and an IP address is used for routing packets across networks but is not unique to the network interface itself.