What hardware device connects different networks at Layer 3?

The hardware device that connects different networks at Layer 3 is a router. Routers operate at the Network Layer (Layer 3) of the OSI model, which is responsible for routing packets between different networks. They utilize IP addresses to determine the best path for data to travel from one network to another.

A router examines the destination IP address of incoming packets and makes decisions about forwarding them to the appropriate next hop on the network. They can connect various types of networks, such as local area networks (LANs) and wide area networks (WANs), allowing different networks to communicate with each other effectively.

In contrast, switches operate at Layer 2 (Data Link Layer) and primarily connect devices within the same network. Hubs function at Layer 1 (Physical Layer) and simply transmit electrical signals to all connected devices without any filtering or routing capability. Bridges also operate at Layer 2 and are used to connect segments of the same network, managing traffic within that network rather than routing between different networks.

Thus, the unique role of routers in facilitating inter-network communication makes them the correct answer for connecting different networks at Layer 3.