Which device is primarily responsible for forwarding packets between different networks?

The device primarily responsible for forwarding packets between different networks is a router. Routers operate at the network layer of the OSI model and are specifically designed to determine the best path for data to travel across interconnected networks. They manage traffic between multiple networks by using routing tables and protocols to identify the most efficient route for the data packets. This functionality allows routers to connect various network segments, making communication possible between devices on different networks.

Switches, while crucial within a local area network (LAN), primarily forward frames based on MAC addresses and operate at the data link layer. Modems serve as a bridge between digital and analog signals, enabling internet connectivity but do not handle inter-network packet forwarding. Access points facilitate wireless communication within a network but do not route packets between different networks. Thus, the router's specialized role ensures the efficient exchange of information across diverse networking environments.