The sole purpose of the Core layer of Cisco's hierarchical internetworking model is:

• A. End-user access control
• B. Policy enforcement
• C. Transit of large amounts of traffic both quickly and reliably
• D. Transit of small data

Answer: (C)

The core layer serves as the high-speed backbone of the network, whose main job is to move large volumes of data quickly and with minimal delay. It’s designed to be fast and highly available, keeping processing light so packets can traverse long distances across the backbone without becoming bottlenecked. Because of that lean, high-capacity role, it doesn’t handle end-user access control or policy enforcement—that’s handled at the edge or distribution layers. It’s built to carry big streams of traffic efficiently, which is why the best description is the transit of large amounts of traffic both quickly and reliably.