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300-410 Practice Question: Runs the following command to troubleshoot a…

A network engineer runs the following command to troubleshoot a Route Redistribution issue:

R1# debug ip ospf adj

And sees the following output:

*Mar  1 00:20:11.456: OSPF: Rcv pkt from 10.1.1.2, Serial0/0/0 : Mismatch Authentication type. Input packet specified type 0, we use type 1
*Mar  1 00:20:11.457: OSPF: Rcv pkt from 10.1.1.2, Serial0/0/0 : Mismatch Authentication type. Input packet specified type 0, we use type 1

What does this output indicate?

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

OSPF authentication is misconfigured; the neighbor is not using authentication while this router is.

The debug ip ospf adj output shows authentication type mismatch. The router expects type 1 (plaintext authentication) but the received packet has type 0 (no authentication). This prevents the OSPF adjacency from forming, which would affect route redistribution if OSPF is not learning routes.

Answer analysis

Option-by-option breakdown

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

  • OSPF adjacency is forming successfully with authentication.

    Why it's wrong here

    The mismatch prevents adjacency from forming.

  • OSPF authentication is misconfigured; the neighbor is not using authentication while this router is.

    Why this is correct

    The router expects authentication type 1, but the neighbor sends type 0, indicating a configuration mismatch.

  • OSPF is redistributing routes correctly but authentication is failing.

    Why it's wrong here

    Redistribution is not relevant here; the adjacency itself is failing.

  • The OSPF process is using MD5 authentication and the neighbor is using plaintext.

    Why it's wrong here

    Type 1 is plaintext; MD5 is type 2. The mismatch is between type 0 and type 1.

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.