Which network device makes decisions based on MAC addresses?

A switch is a network device that makes forwarding decisions based on MAC (Media Access Control) addresses. It operates at Layer 2 of the OSI model, which is the data link layer. When a switch receives a data frame, it analyzes the MAC address contained within that frame to determine which port to send it to for the destination device. This intelligent decision-making allows switches to efficiently manage data traffic within a local area network (LAN), ensuring that data is sent only to the intended recipient, which minimizes unnecessary congestion on the network.

Routers, on the other hand, operate at Layer 3 of the OSI model and make decisions based on IP addresses, directing data between different networks rather than within a single network. Modems, while important for connecting to the internet, primarily convert signals and do not make decisions based on MAC or IP addresses. Firewalls serve as security devices that filter traffic based on rules and policies but do not inherently make decisions based solely on MAC addresses. Thus, the switch is the correct device associated with decisions based on MAC addresses.