Cisco's three-layer model has how many layers?

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

Answer: (B)

Cisco's network design uses three layers: access, distribution, and core. This structure helps organize traffic and policies as networks grow. The access layer is where end devices connect and where VLANs and basic security are implemented. The distribution layer collects traffic from multiple access switches, applies policies, performs inter‑VLAN routing, and provides fault isolation and boundary control to the core. The core layer is the fast backbone that moves traffic between distribution blocks with minimal processing and delay. Because the model is defined as three distinct layers, the correct answer is three. Using fewer layers would combine functions that the distribution layer handles, while adding more layers would introduce unnecessary complexity for this design.