The answer is that the active-time timer is set too low at 3 minutes, causing queries to time out before R2 can reply. In EIGRP, when a router loses a route and transitions to active state, it sends queries to all neighbors and waits for replies within the active-time window. If a neighbor like R2, which has a large number of routes, cannot process and reply to all queries before the timer expires, the querying router declares the route stuck-in-active (SIA) and resets the neighbor relationship. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of how the active-time timer interacts with convergence delays in large topologies—a common trap is assuming a lower timer speeds recovery, when it actually triggers premature SIA events. Remember that the default active-time is 3 minutes, and increasing it (e.g., to 5 minutes) gives slower neighbors more time to reply. Memory tip: “Active-time too low? SIA will grow.”
300-410 EIGRP Troubleshooting Practice Question
This 300-410 practice question tests your understanding of eigrp troubleshooting. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 EIGRP network is experiencing frequent stuck-in-active (SIA) events. Router R1 shows: 'show ip eigrp topology' includes routes in active state for several minutes. R1's configuration: router eigrp 100 timers active-time 3. R2, a neighbor, is reachable but has a large number of routes. What is the root cause?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The active-time timer is set too low (3 minutes), causing queries to time out before R2 can reply.
The active-time timer is set to 3 minutes, which is the default. If a query is sent to a neighbor that takes longer than 3 minutes to reply (due to large topology or slow convergence), the route goes SIA. Reducing the active-time timer can cause premature SIA events.
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 active-time timer is set too low (3 minutes), causing queries to time out before R2 can reply.
Why this is correct
The default active-time is 3 minutes. If R2 has many routes, it may take longer to process queries, leading to SIA.
R2 has a stuck-in-active condition due to a routing loop.
Why it's wrong here
The issue is the timer, not a loop.
✗
R1 has a misconfigured distribute-list that blocks query replies from R2.
Why it's wrong here
No distribute-list is mentioned.
✗
The network has a high latency link that delays query propagation.
Why it's wrong here
While latency can contribute, the primary issue is the timer setting.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
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.
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 active-time timer is set too low (3 minutes), causing queries to time out before R2 can reply. — The active-time timer is set to 3 minutes, which is the default. If a query is sent to a neighbor that takes longer than 3 minutes to reply (due to large topology or slow convergence), the route goes SIA. Reducing the active-time timer can cause premature SIA events.
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.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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