There are___ layers in Cisco's hierarchical internetworking model

• A. Two
• B. Three
• C. Four
• D. Five

Answer: (B)

Three layers form Cisco's hierarchical internetworking model, separating edge access, policy and distribution, and the fast backbone to create a scalable, manageable network.

At the edge, the access layer connects end devices like workstations, printers, and wireless access points. It provides the high port density needed for user connections and implements basic security at the point of entry.

The distribution layer sits between the access and the core and handles tasks that require routing and policy enforcement. It aggregates multiple access-layer switches, routes between VLANs, and applies policies, quality of service, and security controls to ensure consistent behavior across the network.

The core layer is the high-speed backbone. Its job is fast, reliable transport of data between distribution blocks, with minimal processing so switches can forward traffic with maximum efficiency and low latency. It avoids heavy policy work to prevent bottlenecks.

This separation makes networks easier to scale and troubleshoot: you can change or upgrade one layer without forcing changes in the others, while failures tend to be contained more easily. Some smaller networks might collapse two layers into one for simplicity, but the classic Cisco model uses three layers to balance performance, control, and manageability.