hardMultiple ChoiceObjective-mapped
300-410 Practice Question: A DMVPN Phase 3 network with BGP as the routing…
A DMVPN Phase 3 network with BGP as the routing protocol experiences high CPU usage on the hub router R1. The 'show process cpu' command shows high usage by the 'BGP Scanner' process. 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 is receiving a large number of BGP updates from many spokes, causing the BGP Scanner to process many prefixes and consume high CPU.
High BGP Scanner CPU usage can be caused by a large number of prefixes being processed, especially if there are many updates or flapping routes. In a DMVPN network, if spokes are configured to advertise many prefixes or if there is route instability (e.g., due to flapping tunnels), the BGP Scanner process can consume high CPU. Another common cause is that the hub is processing many BGP updates from multiple spokes without proper route filtering or aggregation.
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 is receiving a large number of BGP updates from many spokes, causing the BGP Scanner to process many prefixes and consume high CPU.
Why this is correct
Correct. BGP Scanner processes route updates and can become CPU-bound with many prefixes. Route aggregation or filtering can reduce the load.
- ✗
R1 has a CoPP policy that rate-limits BGP traffic, causing packet drops and retransmissions.
Why it's wrong here
Incorrect. CoPP would affect BGP session stability, not directly cause high BGP Scanner CPU.
- ✗
R1's BGP table is fragmented due to memory issues.
Why it's wrong here
Incorrect. Memory fragmentation would cause other issues, not specifically high BGP Scanner CPU.
- ✗
R1 has 'bgp update-delay' configured, causing delayed processing of updates.
Why it's wrong here
Incorrect. 'bgp update-delay' affects initial convergence, not ongoing CPU usage.
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
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.
About these practice questions
One of 1,966 original 300-410 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
JA
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.