The answer is that the LDP session with neighbor 10.0.0.2 is flapping, as indicated by the repeated UP/DOWN transitions in the debug output. This instability occurs when the Label Distribution Protocol session cannot maintain a stable TCP connection or hello adjacency, often due to mismatched transport addresses, MTU issues, or routing problems that cause the underlying path to oscillate. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your ability to interpret real-time debugging for MPLS LDP session establishment and to distinguish flapping from a single session failure or a graceful restart. A common trap is confusing the UP/DOWN cycle with a normal keepalive timeout; remember that a healthy session stays UP for extended periods, not seconds. Memory tip: “Flapping is a rapid toggle, not a single toggle”—if you see the session state change more than twice in a few seconds, suspect a Layer 1 or Layer 3 issue between the LDP peers.
300-410 MPLS Operations Practice Question
This 300-410 practice question tests your understanding of mpls operations. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 runs the following command to debug MPLS LDP session establishment:
R1# debug mpls ldp session
Output:
*Mar 1 00:01:23.456: LDP: Session with 10.0.0.2:0 (0x1234) is UP
*Mar 1 00:01:24.567: LDP: Session with 10.0.0.2:0 (0x1234) is DOWN
*Mar 1 00:01:25.678: LDP: Session with 10.0.0.2:0 (0x1234) is UP
*Mar 1 00:01:26.789: LDP: Session with 10.0.0.2:0 (0x1234) is DOWN
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 with 10.0.0.2 is flapping
The debug output shows the LDP session with neighbor 10.0.0.2 is flapping (repeatedly going UP and DOWN). This indicates instability in the LDP session.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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 with 10.0.0.2 is flapping
Why this is correct
The session repeatedly transitions between UP and DOWN states, indicating flapping.
The session is not stable; it goes down and up repeatedly.
✗
The LDP session with 10.0.0.2 is using targeted hello
Why it's wrong here
The debug output does not indicate the hello type.
✗
The LDP session with 10.0.0.2 is down permanently
Why it's wrong here
The session comes up multiple times, so it is not permanently down.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
The debug output does not indicate the hello type.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
OSPF neighbours must agree on key parameters.
Router ID selection can affect neighbour relationships and LSDB output.
OSPF cost influences the preferred path.
A route can appear in OSPF information but not become the installed route.
TExam Day Tips
→Check area mismatch first when OSPF adjacency fails.
→Review passive interfaces when a network is advertised but no neighbour forms.
→Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 300-410 question in full detail.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
MPLS Operations — This question tests MPLS Operations — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: The LDP session with 10.0.0.2 is flapping — The debug output shows the LDP session with neighbor 10.0.0.2 is flapping (repeatedly going UP and DOWN). This indicates instability in the LDP session.
What should I do if I get this 300-410 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.