What is the function of a MAC address in a network?

A MAC (Media Access Control) address serves the primary function of uniquely identifying a device on a local network. Every network interface card (NIC) installed in devices, such as computers, routers, and switches, is assigned a unique MAC address by the manufacturer. This address is crucial for communication within a local area network (LAN) because it allows devices to recognize and interact with each other effectively.

When data packets are sent over a network, they are encapsulated within Ethernet frames that include the source and destination MAC addresses. This ensures that information reaches the correct device within the network. The uniqueness of the MAC address helps prevent conflicts between devices and allows for accurate delivery of data.

In contrast, the other options do not accurately reflect the primary function of a MAC address. For instance, while MAC addresses are involved in the local networking layer, they do not facilitate encryption of data packets, monitor network traffic levels, or provide an external IP address, which is allocated through a different mechanism involving routers and Internet Service Providers (ISPs).