N10-009 Question 110
Single answerCollapsed coreA company is moving into a new three-story office with about 120 employees. The network administrator wants a design that reduces equipment costs and management overhead while still providing high-speed switching between floors. There is no separate data center, and the expected traffic load is moderate rather than campus-scale. Which network design best fits this scenario?
- A
Deploy a collapsed core by using a pair of multilayer switches that combine the core and distribution functions
- B
Deploy separate access, distribution, and core layers with dedicated core switches on each floor
- C
Use a bus topology between floor switches to minimize switching complexity
- D
Replace switching with a full mesh of routers between floors for better redundancy
Show answer and explanation
Correct answer: A
Explanation
A collapsed core is a design in which the core and distribution layers are merged, usually by using redundant multilayer switches. This approach is widely recommended for small and medium enterprise networks that do not require the scale of a full three-tier campus model. It reduces hardware costs, simplifies management, and still supports high-speed inter-VLAN and inter-floor traffic. By contrast, a separate core layer is typically reserved for larger environments with higher performance and scalability requirements. This aligns with common hierarchical network design guidance from enterprise networking best practices, including Cisco campus design recommendations, where collapsed core is appropriate when the network is not large enough to justify a dedicated core layer.
- A. Correct.
Correct. A collapsed core design combines the core and distribution layers, typically into one or two high-performance multilayer switches. This is a common best practice for small to medium-sized environments where a full three-tier architecture would add unnecessary cost and complexity. In this scenario, the office size, moderate traffic, and desire to simplify management all align with a collapsed core design.
- B. Incorrect.
Incorrect. A full three-tier design with separate access, distribution, and core layers is more appropriate for larger campus networks that need greater scalability and segmentation across many buildings or very high traffic volumes. For a 120-user office in one building, this would likely be overengineered and more expensive than necessary.
- C. Incorrect.
Incorrect. Bus topology is an outdated physical/network design and is not used to interconnect modern floor switches in an enterprise office. It would create performance and fault-tolerance issues and does not reflect how collapsed core designs are implemented.
- D. Incorrect.
Incorrect. Using a full mesh of routers between floors would increase cost and administrative complexity without matching the company's stated needs. Routers are used for Layer 3 forwarding, but a modern enterprise switching design for a building like this would normally rely on multilayer switches, not a router mesh, for inter-floor connectivity.