Question 2,055 of 2,152

Administrative Distance →hardMultiple ChoiceObjective-mapped

Quick Answer

The answer is that the redistributed routes have a metric of 0, which OSPF treats as unreachable. When redistributing from EIGRP into OSPF, if no seed metric is explicitly configured and the metric-type is set to 1, OSPF defaults to a metric of 0 for those external type 1 routes. OSPF considers a metric of 0 as unreachable, so the routes appear in the database but are never installed in the routing table. This is a classic trap on the Cisco CCNP ENARSI 300-410 exam, testing your understanding that while OSPF defaults to a seed metric of 20 for external type 2 routes, the type 1 default is 0—a subtle but critical distinction. The missing seed metric is the root cause, not a filtering or adjacency issue. Remember the mnemonic: “Type 1 is zero until you give it a hero”—always specify the metric when using metric-type 1.

300-410 Administrative Distance Practice Question

This 300-410 practice question tests your understanding of administrative distance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 configures route redistribution from EIGRP into OSPF. The redistributed routes appear in the OSPF database but are not installed in the routing table of other OSPF routers. Which is the most likely explanation?

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.

Question 1hardmultiple choice

Review the full OSPF breakdown →

A
The OSPF process on the redistributing router does not have a router-id configured.
Why wrong: Missing router-id prevents OSPF from starting, but redistribution would not occur at all.
B
The redistributed routes have a metric of 0, which OSPF treats as unreachable.
OSPF requires a non-zero metric for external routes; a metric of 0 (default for type 1) can cause the route to be ignored.
C
The administrative distance of OSPF external routes (110) is higher than EIGRP (90), so the EIGRP routes are preferred.
Why wrong: AD comparison occurs after route installation; the issue is that the route is not installed at all.
D
The redistribute command is missing the subnets keyword, causing only classful routes to be redistributed.
Why wrong: Missing subnets keyword causes only classful networks to be redistributed, but the routes would still appear in the database.

Full breakdown with real-world context →

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 redistributed routes have a metric of 0, which OSPF treats as unreachable.

When redistributing into OSPF, a seed metric must be specified. If not, OSPF defaults to a metric of 20 for external type 2 routes, but if the metric-type is set to 1, the default metric is 0, which may cause the route to be considered unreachable or not installed.

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 OSPF process on the redistributing router does not have a router-id configured.
Why it's wrong here
Missing router-id prevents OSPF from starting, but redistribution would not occur at all.
✓
The redistributed routes have a metric of 0, which OSPF treats as unreachable.
Why this is correct
OSPF requires a non-zero metric for external routes; a metric of 0 (default for type 1) can cause the route to be ignored.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
✗
The administrative distance of OSPF external routes (110) is higher than EIGRP (90), so the EIGRP routes are preferred.
Why it's wrong here
AD comparison occurs after route installation; the issue is that the route is not installed at all.
✗
The redistribute command is missing the subnets keyword, causing only classful routes to be redistributed.
Why it's wrong here
Missing subnets keyword causes only classful networks to be redistributed, but the routes would still appear in the database.

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.

Trap categories for this question

Keyword trap
Missing subnets keyword causes only classful networks to be redistributed, but the routes would still appear in the database.

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?

Administrative Distance — This question tests Administrative Distance — OSPF neighbours must agree on key parameters..

What is the correct answer to this question?

The correct answer is: The redistributed routes have a metric of 0, which OSPF treats as unreachable. — When redistributing into OSPF, a seed metric must be specified. If not, OSPF defaults to a metric of 20 for external type 2 routes, but if the metric-type is set to 1, the default metric is 0, which may cause the route to be considered unreachable or not installed.

What should I do if I get this 300-410 question wrong?

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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