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300-410 Practice Question: Runs the following command on Router R8: R8# show…

A network engineer runs the following command on Router R8:

R8# show logging | include %LDP-5-NBRCHG

*Mar  1 00:01:10.123: %LDP-5-NBRCHG: LDP Neighbor 10.0.0.2:0 (1) is UP
*Mar  1 00:02:20.456: %LDP-5-NBRCHG: LDP Neighbor 10.0.0.2:0 (1) is DOWN
*Mar  1 00:03:30.789: %LDP-5-NBRCHG: LDP Neighbor 10.0.0.2:0 (1) is UP
*Mar  1 00:04:40.012: %LDP-5-NBRCHG: LDP Neighbor 10.0.0.2:0 (1) is DOWN

Based on this output, what is the most likely problem?

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 LDP session is flapping due to an unstable IGP route to 10.0.0.2.

The output shows LDP neighbor 10.0.0.2 flapping between UP and DOWN. This indicates instability in the LDP session, often due to a flapping IGP route (since LDP depends on IGP reachability), or a misconfiguration of LDP parameters such as hello interval or hold time.

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 LDP session is flapping due to an unstable IGP route to 10.0.0.2.

    Why this is correct

    LDP relies on IGP to establish and maintain neighbors; if the IGP route is flapping, LDP will also flap.

  • The MPLS label space is exhausted.

    Why it's wrong here

    Label exhaustion would cause label allocation failures, not neighbor flapping.

  • The router has a mismatched LDP router ID.

    Why it's wrong here

    A mismatched router ID would prevent the neighbor from coming up at all, not cause flapping.

  • The LDP hello interval is set too high, causing slow detection.

    Why it's wrong here

    A high hello interval would make the session slower to detect changes, but not cause flapping.

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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.