At what OSI layer does a router operate?

A router operates at the Network layer of the OSI model, which is the third layer. This layer is responsible for logical addressing and routing of data packets between devices across different networks. Routers determine the best path for data to travel from the source to the destination, making decisions based on IP addresses.

The Network layer manages packet forwarding through routing tables and protocols such as IP (Internet Protocol), which further facilitates communication among devices in a network. By functioning at this layer, routers enable connectivity across multiple interconnected networks, allowing for efficient data transmission.

In contrast, the Physical layer deals with the physical medium of data transmission, such as cables and signals. The Data link layer is responsible for node-to-node data transfer and handling error correction in the data, while the Transport layer focuses on end-to-end communication, ensuring complete data transfer and managing error recovery and flow control between hosts. Each of these layers has distinct roles that do not encompass the specific routing functionality that is characteristic of the Network layer.