mediumMultiple Choice
Hierarchical Campus Network Design — Choosing Three-Tier vs Collapsed Core
A network architect is designing a campus network for a large university with 10,000+ users. The design must provide high availability, minimize failure domains, and allow for easy scaling of the access layer. The core layer should be resilient and support fast convergence. Which hierarchical design model best meets these requirements?
Quick Answer
The three-tier hierarchical design with access, distribution, and core layers is the correct choice because it provides clear separation of failure domains, allows easy scaling by adding access switches, and supports high availability through redundant links and VRRP for gateway redundancy. For a large campus with 10,000+ users, this model isolates problems at the access layer so they don’t propagate to the core, while the distribution layer aggregates traffic and provides first-hop redundancy. On the ENCOR 350-401 exam, this question tests your understanding of how hierarchical design principles map to real-world scalability and resilience—a common trap is choosing collapsed core for simplicity, but that merges distribution and core functions, creating a single failure domain and limiting future expansion. Remember the memory tip: “Three tiers for three needs—scale, separate, and stabilize.”
⚠ Common exam trap
Cisco often tests the misconception that a collapsed core design is always more efficient for small-to-medium networks, but for a large campus with 10,000+ users, the three-tier model is required to minimize failure domains and allow independent scaling of the access layer.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Three-tier hierarchical design with access, distribution, and core layers, using redundant links and VRRP for gateway redundancy
The three-tier hierarchical design (access, distribution, core) is the correct choice because it provides clear separation of failure domains, allows easy scaling by adding access switches, and supports high availability through redundant links and VRRP (or HSRP/GLBP) for first-hop gateway redundancy. The core layer can be designed with fast-converging protocols like ECMP and BFD to meet the resilience and convergence requirements for a large campus with 10,000+ users.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Three-tier hierarchical design with access, distribution, and core layers, using redundant links and VRRP for gateway redundancy
Why this is correct
A three-tier model with redundant links and VRRP confines failures to individual access or distribution segments, shrinking failure domains while the core provides resilient fast-converging paths. This directly satisfies the university's high-availability, scalability and minimal-failure-domain constraints for 10,000+ users.
- ✗
Collapsed core design with core and distribution combined into one layer
Why it's wrong here
Combining core and distribution into one layer concentrates failure domains and adds latency at the aggregation point, undermining the resilience and fast convergence required at this scale. A collapsed core is tempting for smaller campuses where cost and port density matter more than fault isolation.
- ✗
Flat Layer 2 design with all switches in a single VLAN
Why it's wrong here
A single flat Layer 2 VLAN spanning 10,000+ users creates one enormous broadcast domain and a single failure domain, with no hierarchical core to converge quickly. Flat designs are tempting for small offices where simplicity and minimal hardware outweigh scalability and availability requirements.
- ✗
Leaf-spine design with all switches acting as leafs and spines
Why it's wrong here
Leaf-spine is a data-centre fabric using equal-cost multipathing between every leaf and spine; it does not map onto campus access, distribution and core roles, and complicates scaling of access-layer VLANs. It is tempting because it delivers high availability in data centres, not campus hierarchies.
Go deeper
Related to this question
Learn chapter
Network Access Control and AAA
Key term
High Availability in Enterprise Networks
High Availability in Enterprise Networks is the design principle that ensures network services remain accessible and operational with minimal downtime, even when individual components fail.
Key term
HSRP vs VRRP vs GLBP
HSRP, VRRP, and GLBP are network protocols that provide high availability by allowing multiple routers to work together as a single virtual router, ensuring that if one router fails, another automatically takes over without disrupting the network.
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Same concept, more angles
1 more way this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which two statements about the Cisco Enterprise Campus Architecture are true? (Choose two.)
medium- ✓ A.The distribution layer provides policy-based connectivity and controls traffic flow between access and core layers.
- B.The access layer is responsible for routing between VLANs and providing high-speed switching for the campus backbone.
- ✓ C.The core layer should be designed for high-speed transport and minimal latency, avoiding CPU-intensive features like ACLs.
- D.A two-tier hierarchical design (collapsed core) is recommended for large campus networks with thousands of users.
- E.The core layer should enforce security policies and perform packet inspection to protect the campus network.
Why A: Option A is correct because in the Cisco Enterprise Campus Architecture the distribution layer is the aggregation point that provides policy-based connectivity, inter-VLAN routing, route summarization, and controls traffic flow between the access and core layers. Option C is correct because the core layer is designed as a high-speed transport backbone with minimal latency, so CPU-intensive features such as ACLs, packet inspection, and policy enforcement should be avoided there. Option B is wrong because routing between VLANs and high-speed backbone switching are functions of the distribution and core layers, not the access layer, which primarily provides user/device connectivity and Layer 2 switching with PoE and port security. Option D is wrong because a two-tier collapsed-core design is recommended for smaller campus networks, whereas large campuses with thousands of users typically use a three-tier hierarchical design. Option E is wrong because security policy enforcement and packet inspection belong at the distribution (and access) layers, not the core, which must remain fast and simple.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.