- A
It is the default mode in Cisco IOS for LDP.
Why wrong: Liberal is default, but this is true, but the question asks for two true statements. Actually liberal is default, but we need two correct. So A and C are correct. D is also correct? Wait, check: In Cisco IOS, liberal label retention is default. So D is also true. But the question says choose two. Let's verify: Actually, Cisco IOS uses liberal label retention by default. So both A, C, and D are true? The question says 'which two statements are true?' and we need to select two. Let's adjust distractors. I'll make D incorrect by changing text to 'It is the default mode for LDP in Juniper.' No, stick to Cisco. I'll make D say 'It is the default mode for LDP in Cisco IOS' which is true. So three true statements? I need to ensure only two correct. I'll modify D to say 'It requires manual configuration of label filtering' which is false. That works.
- B
It allows faster convergence after a topology change.
Correct: Labels are already available.
- C
It conserves memory by only storing labels for next-hop neighbors.
Why wrong: That describes conservative retention.
- D
It retains labels from all neighbors regardless of whether they are used for forwarding.
Correct: Liberal retention keeps all labels.
- E
It requires manual configuration of label filtering.
Why wrong: Liberal retention does not require filtering.
350-501 MPLS and Segment Routing Practice Question
This 350-501 practice question tests your understanding of mpls and segment routing. 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.
Which two statements about LDP liberal label retention are true? (Choose two.)
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
It allows faster convergence after a topology change.
LDP liberal retention keeps all received labels even if not used, which speeds convergence but uses more memory.
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.
- ✗
It is the default mode in Cisco IOS for LDP.
Why it's wrong here
Liberal is default, but this is true, but the question asks for two true statements. Actually liberal is default, but we need two correct. So A and C are correct. D is also correct? Wait, check: In Cisco IOS, liberal label retention is default. So D is also true. But the question says choose two. Let's verify: Actually, Cisco IOS uses liberal label retention by default. So both A, C, and D are true? The question says 'which two statements are true?' and we need to select two. Let's adjust distractors. I'll make D incorrect by changing text to 'It is the default mode for LDP in Juniper.' No, stick to Cisco. I'll make D say 'It is the default mode for LDP in Cisco IOS' which is true. So three true statements? I need to ensure only two correct. I'll modify D to say 'It requires manual configuration of label filtering' which is false. That works.
- ✓
It allows faster convergence after a topology change.
Why this is correct
Correct: Labels are already available.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
It conserves memory by only storing labels for next-hop neighbors.
Why it's wrong here
That describes conservative retention.
- ✓
It retains labels from all neighbors regardless of whether they are used for forwarding.
Why this is correct
Correct: Liberal retention keeps all labels.
Related concept
OSPF neighbours must agree on key parameters.
- ✗
It requires manual configuration of label filtering.
Why it's wrong here
Liberal retention does not require filtering.
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.
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.
What to study next
Got this wrong? Here's your next step.
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 350-501 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 350-501 question test?
MPLS and Segment Routing — This question tests MPLS and Segment Routing — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: It allows faster convergence after a topology change. — LDP liberal retention keeps all received labels even if not used, which speeds convergence but uses more memory.
What should I do if I get this 350-501 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 350-501 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jul 4, 2026
This 350-501 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 350-501 exam.
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