- A
The hub router has too many EIGRP neighbors, causing CPU overload and dropped hello packets.
Correct because a high number of neighbors can overwhelm the hub, leading to missed hello packets and adjacency resets, which prolongs convergence.
- B
The EIGRP stub feature is not enabled on the spoke routers.
Why wrong: Incorrect because stub routing helps reduce query propagation, but it does not directly affect hello/hold timer issues or convergence time due to neighbor count.
- C
The EIGRP variance command is configured, causing unequal-cost load balancing.
Why wrong: Incorrect because variance does not affect convergence time; it only affects path selection.
- D
The EIGRP router ID is not configured, so it defaults to the highest loopback IP.
Why wrong: Incorrect because the router ID does not impact convergence time; it is used for route identification.
Quick Answer
The answer is the hub router’s CPU overload caused by too many EIGRP neighbors, which leads to dropped hello packets and adjacency resets. In a large hub-and-spoke topology, the hub must process hello packets, updates, and queries from every spoke; with default hello and hold timers (5 and 15 seconds), a hub managing dozens or hundreds of neighbors can become overwhelmed, causing it to miss hello packets and tear down adjacencies, which then must be re-established—dramatically slowing convergence. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how EIGRP’s default timers interact with scale, and a common trap is assuming slow convergence is due to route summarization or query scoping rather than control-plane congestion. Remember: when you see “hub-and-spoke” and “default timers” together, think “neighbor count overload.” A useful memory tip is “Too many spokes, the hub chokes.”
300-410 EIGRP Troubleshooting Practice Question
This 300-410 practice question tests your understanding of eigrp troubleshooting. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
An engineer is troubleshooting an EIGRP convergence issue. After a link failure, the network takes an unusually long time to converge. The engineer notices that the EIGRP hello and hold timers are set to the default values. The network has many routers in a hub-and-spoke topology. What is the most likely cause of the slow convergence?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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
The hub router has too many EIGRP neighbors, causing CPU overload and dropped hello packets.
In a hub-and-spoke topology, if the hub router has a large number of neighbors, the default EIGRP timers may cause slow convergence because the hub must process many updates. Increasing the hello and hold timers on the hub can help reduce the load, but the issue here is that the timers are default, which can be too fast for a large number of neighbors, causing the hub to drop packets and reset adjacencies.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The hub router has too many EIGRP neighbors, causing CPU overload and dropped hello packets.
Why this is correct
Correct because a high number of neighbors can overwhelm the hub, leading to missed hello packets and adjacency resets, which prolongs convergence.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
The EIGRP stub feature is not enabled on the spoke routers.
Why it's wrong here
Incorrect because stub routing helps reduce query propagation, but it does not directly affect hello/hold timer issues or convergence time due to neighbor count.
- ✗
The EIGRP variance command is configured, causing unequal-cost load balancing.
Why it's wrong here
Incorrect because variance does not affect convergence time; it only affects path selection.
- ✗
The EIGRP router ID is not configured, so it defaults to the highest loopback IP.
Why it's wrong here
Incorrect because the router ID does not impact convergence time; it is used for route identification.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 300-410 question test?
EIGRP Troubleshooting — This question tests EIGRP Troubleshooting — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The hub router has too many EIGRP neighbors, causing CPU overload and dropped hello packets. — In a hub-and-spoke topology, if the hub router has a large number of neighbors, the default EIGRP timers may cause slow convergence because the hub must process many updates. Increasing the hello and hold timers on the hub can help reduce the load, but the issue here is that the timers are default, which can be too fast for a large number of neighbors, causing the hub to drop packets and reset adjacencies.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
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