hardMultiple ChoiceObjective-mapped
300-410 Practice Question: A DMVPN Phase 3 network uses BGP for routing…
A DMVPN Phase 3 network uses BGP for routing between hubs and spokes. R1 (hub) and R2 (spoke) have an eBGP peering. R2 advertises a prefix 192.168.1.0/24 to R1. R3 (another spoke) receives this prefix via R1 but with a higher local preference than expected, causing R3 to prefer the path through R1 even though a direct spoke-to-spoke tunnel exists. What is the root cause?
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
✓
R1 has a route-map that sets local preference to 200 for prefixes received from R2, causing R3 to prefer the path through R1 over the direct path.
BGP local preference is manipulated on the hub (R1) using route-maps or policy, causing the prefix to have a higher local preference when advertised to other spokes. This overrides the normal BGP path selection and forces traffic through the hub, even if a direct spoke-to-spoke tunnel is available.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
R1 has a route-map that sets local preference to 200 for prefixes received from R2, causing R3 to prefer the path through R1 over the direct path.
Why this is correct
Correct. BGP local preference is propagated to iBGP peers. If R1 sets a high local preference on routes from R2, R3 will prefer the path via R1, even if a direct spoke-to-spoke tunnel is available.
- ✗
R3 has a static route pointing to R1 for 192.168.1.0/24, overriding BGP.
Why it's wrong here
Incorrect. Static routes have higher administrative distance than BGP, but the issue is about BGP path selection, not static routes.
- ✗
NHRP redirect is disabled on R1, preventing spoke-to-spoke tunnel establishment.
Why it's wrong here
Incorrect. NHRP redirect is needed for Phase 3, but the issue is BGP path selection, not tunnel establishment.
- ✗
R2 is advertising the prefix with a MED of 0, causing R3 to prefer the path through R1.
Why it's wrong here
Incorrect. MED is compared only when paths are from the same AS, and local preference is evaluated before MED. The issue is local preference manipulation.
Go deeper
Related to this question
Learn chapter
Introduction to ENARSI Exam and Network Fundamentals
Key term
DMVPN Phase 3
DMVPN Phase 3 is a Cisco networking technology that allows branch offices to connect directly to each other without always going through a central hub, but with smarter routing that lets the hub control the traffic paths more efficiently.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 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 300-410 exam.