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300-410 Practice Question: Which loop prevention mechanism is used by…

Which loop prevention mechanism is used by default when redistributing between two OSPF processes?

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

Route tagging with default tag 0

When redistributing between OSPF processes, Cisco IOS uses route tagging (tag field in the OSPF external LSA) to prevent loops, but the default tag value is 0 unless explicitly set.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • Split horizon

    Why it's wrong here

    Split horizon is a RIP and EIGRP mechanism, not used in OSPF redistribution.

  • Route tagging with default tag 0

    Why this is correct

    Route tagging allows an OSPF process to identify and filter routes it originated, preventing loops; the default tag is 0.

  • Poison reverse

    Why it's wrong here

    Poison reverse is used in distance vector protocols like RIP, not OSPF.

  • Hold-down timers

    Why it's wrong here

    Hold-down timers are used in RIP and EIGRP, not in OSPF redistribution.

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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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.