Which network device operates at both the data link and network layers of the OSI model, and is responsible for routing data packets between networks? 

A Router operates at both the Data Link layer (Layer 2) and the Network layer (Layer 3) of the OSI model. It is responsible for routing data packets between different networks by determining the best path based on IP addresses. Routers manage traffic within networks by forwarding packets and ensuring that data is efficiently transmitted to its destination. They also offer features like packet filtering, network address translation (NAT), and traffic segmentation, making them essential in both small and large-scale networks. Why Other Options are Incorrect: A) Hub: A Hub operates only at the Physical layer (Layer 1) and does not route data packets or operate at higher layers. B) Bridge: A Bridge operates at the Data Link layer (Layer 2) and is used to connect multiple LAN segments but cannot route between different networks. C) Switch: A Switch operates primarily at the Data Link layer (Layer 2) and sometimes at Layer 3 (Layer 3 switches), but traditional switches do not perform routing between different networks like routers do. E) Gateway: A Gateway operates at higher layers of the OSI model, typically up to the Application layer, and is used to translate between different protocols rather than simply routing packets.