At which layer of the OSI model do routers operate?

Routers operate at Layer 3 of the OSI model, which is known as the Network layer. This layer is responsible for the logical addressing and routing of data packets between devices across different networks. Routers use IP addresses to determine the best path for forwarding packets to their destination, enabling communication not just within a single local area network but also between multiple networks.

The Network layer plays a critical role in packet forwarding and routing protocols, something that routers are specifically designed to handle. They make decisions based on the destination IP address contained in the packet header and utilize various routing algorithms and protocols to determine the best available route.

While other layers, like the Data Link layer (Layer 2), deal with frame forwarding within the same local network using MAC addresses, and the Physical layer (Layer 1), which concerns the actual transmission of raw bit streams over physical mediums, do involve networking tasks, they do not encompass the routing functionality that is essential to how routers operate. Additionally, the Transport layer (Layer 4) is involved with end-to-end communication and error recovery but does not handle the routing of packets between networked devices.