350-601 OSPF neighbor formation Practice Question
A data center architect is designing a spine-leaf fabric with OSPF as the underlay routing protocol. Which two statements about OSPF in this design are correct? (Choose two.)
⚠ Common exam trap
Cisco often tests the misconception that OSPF must be replaced by BGP in VXLAN EVPN fabrics, but the correct understanding is that OSPF serves as the underlay and BGP as the overlay, and they can operate together. Also, candidates may think that all three statements (A, B, C) are correct, but only two are correct per the question's requirement.
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
✓
OSPF neighbors are formed between leaf and spine switches over the fabric links.
In a spine-leaf fabric using OSPF as the underlay, OSPF neighbors are formed directly between leaf and spine switches over the physical fabric links. Option B is correct because OSPF supports ECMP by default, enabling load balancing across multiple equal-cost paths in the fabric. Option C is incorrect: while passive interfaces are often configured on server-facing ports to prevent OSPF neighbor formation with servers, the question asks for two correct statements about OSPF in the design, and the other two options (A and B) are more fundamental to OSPF operation in the underlay. Options D and E are clearly incorrect; OSPF can coexist with BGP in VXLAN EVPN, and OSPF areas can be the same across leaf and spine switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
OSPF neighbors are formed between leaf and spine switches over the fabric links.
Why this is correct
Correct. OSPF neighbors are formed between leaf and spine switches over the fabric links, establishing Layer 3 adjacency for the underlay.
- ✓
OSPF supports ECMP by default, which is essential for load balancing in the fabric.
Why this is correct
Correct. OSPF supports ECMP by default, enabling load balancing across multiple spine switches, which is critical for fabric performance.
- ✗
Passive interfaces are configured on the server-facing ports of leaf switches.
Why it's wrong here
Incorrect. While passive interfaces are commonly configured on server-facing ports, this is a general best practice and not specifically a fundamental OSPF underlay statement. Also, the question asks for two correct statements, and A and B are more directly relevant.
- ✗
OSPF must be replaced by BGP in a VXLAN EVPN fabric.
Why it's wrong here
Incorrect. OSPF can be used as the underlay protocol in a VXLAN EVPN fabric; BGP is used for the overlay, not as a replacement.
- ✗
OSPF areas must be different for leaf and spine switches to prevent routing loops.
Why it's wrong here
Incorrect. OSPF areas can be the same for leaf and spine switches; different areas are not required to prevent routing loops.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-601 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 350-601 exam.