Which device is used to connect different networks and operate on Layer 3 of the OSI model?

The device that is used to connect different networks and operates on Layer 3 of the OSI model is the router. Routers are essential in managing traffic between different networks and forwarding data packets based on their IP addresses. This capability allows them to determine the best path for data to travel across interconnected networks.

At Layer 3, routers process logical addressing schemes such as IP addresses, enabling them to make forwarding decisions based on destination addresses. This is fundamentally different from devices operating at lower layers of the OSI model. For example, switches work at Layer 2 and primarily manage traffic within the same local network using MAC addresses, while hubs and bridges operate even lower, not focusing on network layer functions such as routing between different subnets.

The router's ability to facilitate communications between multiple network segments makes it a crucial component in both local and wide area networks. In summary, the router's operation at Layer 3 is what distinguishes it in connecting different networks effectively.