350-401 Architecture Practice Question
A network architect is designing a Fabric-enabled campus with Cisco SD-Access and must choose the optimal underlay routing protocol. The fabric will use VXLAN data-plane encapsulation, and the architect wants minimal configuration on the intermediate underlay devices while supporting fast convergence and equal-cost multipath. Which underlay routing approach should be recommended?
⚠ Common exam trap
The trap here is assuming any dynamic routing protocol works equally well as an SD-Access underlay, when the automated fabric workflow specifically deploys IS-IS for minimal configuration.
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
✓
Use Cisco SD-Access fabric with an IS-IS underlay automatically enabled by the fabric provisioning workflow.
Cisco SD-Access uses an IS-IS underlay that is automatically provisioned by Cisco DNA Center, reducing manual configuration on intermediate devices while supporting fast convergence and ECMP. OSPFv2 and eBGP require explicit per-device configuration and are not the automated fabric underlay. RIPng is unsuitable due to hop limits and slow convergence.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Enable RIPng on all underlay devices to provide simple hop-count-based routing.
Why it's wrong here
RIPng is a distance-vector protocol with a 15-hop limit and slow convergence, and it is unsuitable for a modern SD-Access underlay. It would also require manual configuration on intermediate devices and does not scale or converge quickly enough for fabric traffic, so it does not meet the requirements.
- ✓
Use Cisco SD-Access fabric with an IS-IS underlay automatically enabled by the fabric provisioning workflow.
Why this is correct
In Cisco SD-Access, the recommended underlay for a Fabric-enabled campus is IS-IS, which is automatically configured by the fabric provisioning workflow through Cisco DNA Center. IS-IS supports fast convergence and ECMP, and the automated deployment minimizes manual configuration on intermediate underlay switches, matching the stated requirement for minimal configuration.
- ✗
Deploy eBGP between all underlay switches using unique autonomous system numbers per device.
Why it's wrong here
eBGP with unique AS numbers per device is used in some data center designs, but it introduces complex policy and peering configuration on every switch. For a campus SD-Access fabric, this is not the automated underlay approach and would require significant manual configuration, failing the minimal-configuration objective.
- ✗
Configure OSPFv2 in a single area on all underlay devices, including the fabric edge and border nodes.
Why it's wrong here
OSPFv2 can provide routing in the underlay, but it requires explicit area design, interface-level configuration, and neighbor relationships on every underlay device, which increases operational overhead. The scenario asks for minimal configuration on intermediate devices, so a protocol that needs per-interface tuning and area planning is less optimal than an automated fabric underlay.
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
SDN Controllers and Cisco ACI
Key term
Cisco Virtual Topology System
Cisco Virtual Topology System is a software-defined networking solution that creates and manages virtual network overlays across physical and virtual infrastructure for enterprise networks.
Key term
Fabric Fundamentals
Fabric Fundamentals is the set of core concepts behind a network fabric, where switches and routers form a single logical system that simplifies traffic forwarding and automation.
About these practice questions
This 350-401 question is part of Courseiva's 1,923-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
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.