350-401 Architecture Practice Question
A network engineer is designing a high-availability solution for a data center using Cisco Application Centric Infrastructure (ACI). The engineer wants to ensure that the fabric can continue to operate if a spine switch fails, and that traffic is load-balanced across all available paths. Which statement accurately describes the ACI fabric architecture?
⚠ Common exam trap
The trap here is assuming ACI relies on STP or a standby spine, when it actually uses a full-mesh active-active spine-leaf architecture.
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
✓
ACI uses a spine-leaf topology where every leaf connects to every spine, and a failed spine switch reduces capacity but does not cause an outage.
ACI uses a spine-leaf topology where all leaf switches connect to all spine switches, providing active-active forwarding. A failed spine reduces overall capacity but does not cause an outage because other spines continue to forward traffic. This design ensures high availability and load balancing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
ACI uses a spine-leaf topology where every leaf connects to every spine, and a failed spine switch reduces capacity but does not cause an outage.
Why this is correct
In ACI, leaf switches connect to all spine switches, forming a full-mesh at the spine level. If a spine fails, the remaining spines continue to forward traffic, so the fabric remains operational. This provides high availability and load balancing across all available paths, meeting the design requirements.
- ✗
ACI uses a single spine switch for all traffic, and redundancy is achieved through a standby spine that takes over on failure.
Why it's wrong here
ACI does not use a single active spine with a standby. All spine switches are active and forward traffic simultaneously. The fabric is designed for active-active operation, and there is no standby spine. This option misrepresents the ACI architecture and its high-availability model.
- ✗
ACI uses a traditional Spanning Tree Protocol (STP) to prevent loops, and a failed spine switch causes a full fabric outage.
Why it's wrong here
ACI does not use STP; it uses a spine-leaf architecture with an overlay protocol (VXLAN) and a distributed control plane (IS-IS). The fabric is designed for high availability, and a failed spine switch does not cause a full outage. STP is not part of the ACI fabric forwarding model.
- ✗
ACI uses a ring topology for the fabric, and a failed spine switch breaks the ring, causing a partial outage.
Why it's wrong here
ACI does not use a ring topology; it uses a spine-leaf topology. A ring would be used in some other architectures, but not in ACI. In ACI, the spine layer is a full mesh with the leaf layer, and a spine failure does not break connectivity because other spines are available.
Go deeper
Related to this question
Learn chapter
Spine-Leaf and Software-Defined Network Architectures
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.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.