Which layer of the OSI model is responsible for routing?

The OSI (Open Systems Interconnection) reference model divides network communication into seven layers, each with a distinct, non-overlapping job. Selecting a path for data across multiple interconnected networks — using logical addressing and routing tables — is the responsibility defined for Layer 3, the Network Layer, in the OSI specification.

The question asks which layer moves data across separate, interconnected networks by choosing a path between them — this is exactly the Network Layer's defined role, so the Network Layer is the layer being asked about.

• Data Link Layer (Layer 2) handles delivery of frames between two directly connected nodes on the same network segment, using physical/MAC addressing — a different scope than moving data between separate networks.

• Transport Layer (Layer 4) handles end-to-end delivery of data segments between processes on the source and destination hosts, assuming a network path already exists between them.

• Application Layer (Layer 7) provides the interface through which user software accesses network services, operating above the layers concerned with choosing a network path.

Because selecting a path for data across interconnected networks is uniquely defined as the Network Layer's job in the OSI model, Network Layer is the correct answer.