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300-410 Practice Question: Is troubleshooting a redistribution issue between…

A network engineer is troubleshooting a redistribution issue between EIGRP and OSPF. Router R1 redistributes EIGRP routes into OSPF. The engineer configured a summary route 10.0.0.0/8 using the 'summary-address' command under the OSPF process. After the configuration, OSPF neighbors lose connectivity to the 10.1.0.0/16 subnet, which is one of the component routes. What is the most likely cause?

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 summary route 10.0.0.0/8 is not being generated because the component routes are not all present in the OSPF database.

The issue is that the summary-address command in OSPF can suppress the advertisement of more specific routes, but if the summary route is not installed due to a missing component or metric issue, it can cause a routing black hole.

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 summary-address command on R1 is configured with the 'tag' keyword, causing the summary to be ignored by other routers.

    Why it's wrong here

    Incorrect. The tag keyword does not cause the summary to be ignored; it is used for route tagging.

  • The summary route 10.0.0.0/8 is not being generated because the component routes are not all present in the OSPF database.

    Why this is correct

    Correct. In OSPF, the summary-address command generates a summary only if at least one component route exists in the OSPF database. If the component route is missing due to redistribution issues, the summary may not be generated, and the specific routes may be suppressed.

  • The OSPF neighbor relationship is down due to a mismatch in area IDs.

    Why it's wrong here

    Incorrect. The symptom is specific to one subnet; neighbor relationships are likely up.

  • The engineer forgot to configure the 'network' command for the summary route under OSPF.

    Why it's wrong here

    Incorrect. The summary-address command does not require a network statement; it is applied to redistributed routes.

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.

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Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

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