Question 922 of 2,152
IPv6 First Hop SecurityhardMultiple ChoiceObjective-mapped

Fix EIGRP OSPFv3 Redistribution Failure Due to Process ID Mismatch

This 300-410 practice question tests your understanding of ipv6 first hop security. 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.

A network engineer is troubleshooting IPv6 redistribution between EIGRP and OSPFv3 on Router R1. Routes from OSPFv3 are being redistributed into EIGRP, but they are not appearing in the EIGRP topology table. Router R1 has the following relevant configuration:

router eigrp Test

address-family ipv6 unicast redistribute ospf 1 metric 10000 100 255 1 1500 !

Router R2 shows: show ipv6 eigrp topology output does not include any OSPF-derived routes. What is the root cause?

Quick Answer

The answer is an OSPFv3 process ID mismatch in the redistribute command. The configuration shows `redistribute ospf 1` under the EIGRP IPv6 address-family, but the actual OSPFv3 process running on the router must match that number; if the OSPFv3 process ID is different or the process is not active, the redistribution fails silently—routes never enter the EIGRP topology table. This exact scenario tests your understanding of how EIGRP OSPFv3 redistribution depends on precise process ID alignment, a common trap on the Cisco CCNP ENARSI 300-410 exam where candidates overlook that the redistribute statement references a specific OSPFv3 process, not the protocol generically. The failure produces no error log, so you must verify both the OSPFv3 process ID with `show ipv6 ospf` and the redistribute command syntax. Memory tip: “Match the ID or the route will hide”—always confirm the process number in both the redistribute line and the running OSPFv3 configuration.

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 OSPFv3 process ID in the redistribute command does not match the actual OSPFv3 process ID running on the router.

Option B is correct because the redistribute ospf 1 command references OSPFv3 process ID 1, but if the actual OSPFv3 process ID running on Router R1 is different (e.g., 100), the redistribution will silently fail—no routes are injected into EIGRP. The process ID must match exactly for redistribution to occur.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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 EIGRP metric values are too high, causing the routes to be considered unreachable.

    Why it's wrong here

    Metric values are within typical ranges; they would still appear in the topology table.

  • The OSPFv3 process ID in the redistribute command does not match the actual OSPFv3 process ID running on the router.

    Why this is correct

    If the process ID is wrong, the redistribution command does not match any OSPFv3 process, and no routes are redistributed.

    Related concept

    Read the scenario before looking for a memorised answer.

  • The routes from OSPFv3 are external, and EIGRP does not redistribute external OSPF routes by default.

    Why it's wrong here

    The redistribute command includes all OSPF routes unless filtered.

  • The EIGRP address-family is not configured with a router ID, preventing redistribution.

    Why it's wrong here

    EIGRP for IPv6 does not require a router ID for redistribution.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the requirement for matching process IDs in redistribution commands, leading candidates to overlook that the redistribute statement references a specific OSPF process that must be active and correctly numbered.

Trap categories for this question

  • Command / output trap

    The redistribute command includes all OSPF routes unless filtered.

Detailed technical explanation

How to think about this question

In Cisco IOS, the redistribute ospf [process-id] command under EIGRP IPv6 address-family requires the OSPFv3 process ID to match the router ospf [process-id] configuration. If mismatched, the router logs a warning like 'OSPF process not found' but does not drop the configuration—it simply ignores the redistribution. This is a common misconfiguration in multi-process environments where OSPFv3 process IDs are not standardized.

KKey Concepts to Remember

  • Read the scenario before looking for a memorised answer.
  • Find the constraint that changes the correct option.
  • Eliminate answers that are true in general but not in this case.

TExam Day Tips

  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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.

Visual reference

R1 R2 R3 R4 10 100 10 100 OSPF picks R1→R2→R4 (cost 20) over R1→R3→R4 (cost 200)

Quick reference

Routing Protocol Comparison

ProtocolMetricMax HopsAlgorithmType
RIP v2Hop count15Bellman-FordDistance vector
OSPFCost (bandwidth)UnlimitedDijkstra (SPF)Link state
EIGRPComposite metricUnlimitedDUALHybrid
IS-ISCostUnlimitedDijkstraLink state
BGPPolicy / attributesUnlimitedPath vectorPath vector

RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.

What to study next

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FAQ

Questions learners often ask

What does this 300-410 question test?

IPv6 First Hop Security — This question tests IPv6 First Hop Security — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The OSPFv3 process ID in the redistribute command does not match the actual OSPFv3 process ID running on the router. — Option B is correct because the redistribute ospf 1 command references OSPFv3 process ID 1, but if the actual OSPFv3 process ID running on Router R1 is different (e.g., 100), the redistribution will silently fail—no routes are injected into EIGRP. The process ID must match exactly for redistribution to occur.

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

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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Last reviewed: Jul 4, 2026

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