Question 13

Routing occurs at the Network layer.

The routing function of a router takes place at the Network layer of the OSI model, where it is responsible for forwarding data packets between different IP subnets.

A) Network layer

This option is correct because the Network layer (Layer 3) is specifically designed for routing and forwarding packets across multiple networks. Routers operate at this layer to determine the best path for data to travel from the source subnet to the destination subnet.

B) Transport layer

This option is incorrect as the Transport layer (Layer 4) is responsible for end-to-end communication, flow control, and error recovery, rather than routing between subnets. It ensures that data is delivered error-free and in sequence but does not handle routing decisions.

C) Application layer

This option is incorrect because the Application layer (Layer 7) focuses on providing network services directly to end-user applications. It does not involve routing or forwarding data between IP subnets; its role is to enable user applications to communicate over the network.

D) Data link layer

This option is incorrect as the Data link layer (Layer 2) deals with the physical addressing and the transfer of data between adjacent network nodes within the same subnet. While it is essential for local network communication, it does not manage routing between different subnets.

Conclusion

The Network layer is the only layer in the OSI model that is involved in routing between different IP subnets, which makes Option A the definitive correct choice. All other options pertain to different functions and layers of the OSI model that do not encompass the routing capabilities of a router.