- A
Spine-leaf, because it provides equal-cost multipath (ECMP) for all leaf-to-leaf traffic.
Correct because spine-leaf uses ECMP to forward traffic between any two leaf switches with predictable latency, supporting east-west traffic efficiently.
- B
Three-tier, because it offers more redundancy with multiple aggregation layers.
Why wrong: Incorrect because three-tier designs often have bottlenecks at the aggregation layer for east-west traffic, and redundancy is not inherently better.
- C
Spine-leaf, because it supports legacy spanning tree protocols.
Why wrong: Incorrect because spine-leaf typically uses routing (e.g., BGP) rather than STP, and legacy STP is not a benefit.
- D
Three-tier, because it is easier to manage with traditional VLANs.
Why wrong: Incorrect while three-tier may be familiar, it does not optimize east-west traffic; spine-leaf is preferred for modern data centers.
Quick Answer
The answer is spine-leaf architecture, because it is specifically designed to optimize east-west traffic through equal-cost multipath (ECMP) routing. In a spine-leaf design, every leaf switch connects to every spine switch, creating a full mesh that allows traffic between any two leaf switches to traverse multiple parallel paths of equal cost. This eliminates the bottlenecks and unpredictable latency found in a traditional three-tier model, where east-west traffic must hairpin through the aggregation and core layers, making spine-leaf far more suitable for server virtualization traffic that frequently moves between hypervisors. On the ENCOR 350-401 exam, this question tests your understanding of data center fabric design and the limitations of hierarchical models for modern traffic flows—a common trap is assuming three-tier is always better for scalability. Remember the memory tip: “Spine-leaf for east-west, three-tier for north-south.”
350-401 Enterprise Network Design Practice Question
This 350-401 practice question tests your understanding of enterprise network design. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company is deploying a new data center and needs to choose between a three-tier (core, aggregation, access) and a spine-leaf architecture. The network engineer is concerned about east-west traffic patterns for server virtualization. Which architecture is most suitable and why?
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
Spine-leaf, because it provides equal-cost multipath (ECMP) for all leaf-to-leaf traffic.
Spine-leaf architecture is most suitable for east-west traffic patterns because it provides a full mesh of connections between leaf switches and spine switches, enabling equal-cost multipath (ECMP) routing. This allows all leaf-to-leaf traffic to traverse multiple parallel paths with equal cost, maximizing bandwidth utilization and minimizing latency, which is critical for server virtualization traffic that often moves between hypervisors.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Spine-leaf, because it provides equal-cost multipath (ECMP) for all leaf-to-leaf traffic.
Why this is correct
Correct because spine-leaf uses ECMP to forward traffic between any two leaf switches with predictable latency, supporting east-west traffic efficiently.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Three-tier, because it offers more redundancy with multiple aggregation layers.
Why it's wrong here
Incorrect because three-tier designs often have bottlenecks at the aggregation layer for east-west traffic, and redundancy is not inherently better.
- ✗
Spine-leaf, because it supports legacy spanning tree protocols.
- ✗
Three-tier, because it is easier to manage with traditional VLANs.
Why it's wrong here
Incorrect while three-tier may be familiar, it does not optimize east-west traffic; spine-leaf is preferred for modern data centers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that three-tier architecture is more redundant or easier to manage, but the key trap here is that candidates may overlook how east-west traffic patterns require non-blocking, low-latency paths that only a spine-leaf design with ECMP can provide.
Detailed technical explanation
How to think about this question
In a spine-leaf design, ECMP is typically implemented using a routing protocol such as OSPF or BGP, where each leaf switch has multiple equal-cost paths to any other leaf switch via the spine switches. For server virtualization, this ensures that traffic between VMs on different leaf switches can utilize all available spine links, avoiding congestion and providing predictable performance. Real-world deployments often use BGP as the underlay routing protocol with a private AS number per leaf to enable fast convergence and scalability.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 350-401 question test?
Enterprise Network Design — This question tests Enterprise Network Design — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Spine-leaf, because it provides equal-cost multipath (ECMP) for all leaf-to-leaf traffic. — Spine-leaf architecture is most suitable for east-west traffic patterns because it provides a full mesh of connections between leaf switches and spine switches, enabling equal-cost multipath (ECMP) routing. This allows all leaf-to-leaf traffic to traverse multiple parallel paths with equal cost, maximizing bandwidth utilization and minimizing latency, which is critical for server virtualization traffic that often moves between hypervisors.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways 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. An enterprise is migrating its data center to a leaf-spine architecture to support high east-west traffic between servers. The design must provide non-blocking forwarding and allow for easy scaling by adding more spines. Which characteristic is essential for the spine switches in this design?
medium- A.Spine switches must run Spanning Tree Protocol (STP) to prevent loops
- ✓ B.Spine switches must support high port density and high forwarding capacity, and act as Layer 3 routers
- C.Spine switches must be connected to each other to provide redundancy
- D.Spine switches must perform NAT to translate between VLANs
Why B: In a leaf-spine architecture designed for non-blocking forwarding and high east-west traffic, spine switches must act as Layer 3 routers with high port density and forwarding capacity. This allows them to perform Equal-Cost Multi-Path (ECMP) routing, which distributes traffic across all available uplinks without blocking, ensuring that any leaf can reach any other leaf with predictable latency and full bandwidth utilization.
Last reviewed: Jun 24, 2026
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.
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