The root cause is that the redistributed OSPF route is a summary, which triggers EIGRP queries that go unanswered, leading to the stuck-in-active (SIA) state. When OSPF redistributes a summary route into EIGRP, the EIGRP router sends queries to all neighbors for that prefix; if a neighbor lacks a feasible successor or a route back, it never replies, causing the Active timer to expire and the route to become SIA. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of EIGRP query scoping and the dangers of injecting summarized routes from another protocol—a common trap is assuming the issue is a metric mismatch or a simple redistribution loop. The fix involves either disabling automatic summarization or configuring the problematic neighbor as a stub router to limit query propagation. Memory tip: “Summaries can silence replies—stub stops the queries.”
300-410 Route Redistribution Practice Question
This 300-410 practice question tests your understanding of route redistribution. 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.
After redistributing OSPF into EIGRP, an EIGRP router becomes stuck-in-active (SIA) for certain routes. Router R1 config:
router eigrp 100
redistribute ospf 1 metric 10000 100 255 1 1500
!
router ospf 1
redistribute eigrp 100 subnets
R1# show ip eigrp topology 10.0.0.0/8
IP-EIGRP (AS 100): Topology entry for 10.0.0.0/8
State: Active, 0:01:15, Reply count: 0
Originating router: 10.1.1.1
Last sent query: 10.1.1.2
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The redistributed OSPF route is a summary that causes EIGRP queries to go unanswered, leading to SIA.
The EIGRP route for 10.0.0.0/8 is in Active state, meaning it is waiting for replies from neighbors. The redistribution from OSPF may be injecting a summary route that causes a query to be sent to all neighbors, but one neighbor may not have a route back, causing the query to be unanswered. The fix is to ensure that the redistributed routes are not summarized or to use a stub router to limit query scope.
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 redistributed OSPF route is a summary that causes EIGRP queries to go unanswered, leading to SIA.
Why this is correct
Summary routes can cause queries to propagate widely; if a neighbor has no route, the query times out.
The EIGRP metric is too high, causing the route to be unreachable.
Why it's wrong here
Metric does not cause SIA; SIA is about query replies.
✗
The OSPF redistribution is missing the subnets keyword, causing classful behavior.
Why it's wrong here
Missing subnets would not cause SIA; it would affect route installation.
✗
The EIGRP AS number is mismatched between routers.
Why it's wrong here
AS mismatch would prevent neighbor formation, not cause SIA.
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.
Route Redistribution — This question tests Route Redistribution — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The redistributed OSPF route is a summary that causes EIGRP queries to go unanswered, leading to SIA. — The EIGRP route for 10.0.0.0/8 is in Active state, meaning it is waiting for replies from neighbors. The redistribution from OSPF may be injecting a summary route that causes a query to be sent to all neighbors, but one neighbor may not have a route back, causing the query to be unanswered. The fix is to ensure that the redistributed routes are not summarized or to use a stub router to limit query scope.
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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