The answer is Liberal Label Retention mode. This is the default label retention mode on Cisco IOS-XE routers for MPLS LDP, meaning the router retains all label bindings received from any LDP neighbor, regardless of whether that neighbor is the next hop for the corresponding Forwarding Equivalence Class (FEC). The technical rationale is that liberal retention allows for faster convergence; if a next-hop changes, the router already has the label binding for the new path and can immediately use it without waiting for a new label advertisement. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of MPLS label retention modes and their impact on memory versus convergence speed. A common trap is confusing liberal retention with the conservative mode, which only stores labels from the next-hop neighbor—liberal uses more memory but offers quicker failover. For a memory tip, think "Liberal Loves Lots of Labels" to recall that it keeps all bindings from all neighbors.
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.
In MPLS LDP, what is the default label retention mode on Cisco IOS-XE routers?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Liberal Label Retention mode
The default label retention mode is Liberal, meaning that a router retains all label bindings received from neighbors, even if the neighbor is not the next hop for the FEC.
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.
✓
Liberal Label Retention mode
Why this is correct
Liberal retention is the default; it allows faster convergence but uses more memory.
Conservative retention only retains labels from the next hop, but it is not the default.
✗
Ordered Label Retention mode
Why it's wrong here
Ordered is a label distribution control mode, not a retention mode.
✗
Independent Label Retention mode
Why it's wrong here
Independent is a label distribution control mode, not a retention mode.
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.
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: Liberal Label Retention mode — The default label retention mode is Liberal, meaning that a router retains all label bindings received from neighbors, even if the neighbor is not the next hop for the FEC.
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.
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