mediumMultiple Choice
300-410 Practice Question: Runs the following command to debug MPLS LDP…
A network engineer runs the following command to debug MPLS LDP label advertisements:
R1# debug mpls ldp labels
Output:
*Mar 1 00:01:23.456: LDP: Sent label mapping for 192.168.1.0/24, label 101 *Mar 1 00:01:23.789: LDP: Received label mapping for 192.168.2.0/24, label 201 *Mar 1 00:01:24.012: LDP: Sent label mapping for 10.0.0.0/8, label 102 *Mar 1 00:01:24.345: LDP: Received label mapping for 10.0.0.0/8, label 202
What does this output indicate?
⚠ Common exam trap
300-410 often tests the interpretation of LDP debug output, and candidates may misread 'Sent' and 'Received' as session issues or implicit null usage.
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
✓
LDP label bindings are being exchanged between R1 and its LDP neighbor
The debug output shows R1 sending and receiving label mappings for various prefixes, indicating that LDP label bindings are being exchanged with its LDP neighbor. This is normal LDP operation for establishing label-switched paths.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
LDP label bindings are being exchanged between R1 and its LDP neighbor
Why this is correct
The debug confirms R1 and its LDP peer are exchanging label bindings: R1 advertises local labels (101, 102) for its prefixes while receiving remote mappings (201, 202) for the same or different destinations. This bidirectional mapping satisfies the stem's requirement to verify LDP label advertisement between neighbours.
- ✗
R1 is only receiving label mappings, not sending any
Why it's wrong here
The output contains both sent and received mappings, so R1 is advertising as well as learning labels. One-way reception is tempting because asymmetric advertisement is a genuine LDP fault, and would be the answer if only Received lines appeared in the debug.
- ✗
The LDP session is down
Why it's wrong here
Sent and received label mappings prove the LDP session is up and exchanging advertisements in both directions. Session-down is tempting because LDP troubleshooting often starts there, and it would be correct if the debug showed no messages, or session hold-timer expiry notices.
- ✗
R1 is using implicit null label for 10.0.0.0/8
Why it's wrong here
The output shows explicit label mappings sent and received, including label 202 for 10.0.0.0/8, so no implicit null is in use. Implicit null is tempting because it is a real LDP behaviour for directly connected prefixes, and would be the answer if a mapping showed label 3 or no label.
Go deeper
Related to this question
Learn chapter
EIGRP Neighbor Adjacency and Basics
Key term
LDP Protocol
LDP, or Label Distribution Protocol, is a protocol that routers use to automatically exchange labels that enable MPLS (Multiprotocol Label Switching) to create fast, efficient paths for data packets across a network.
Key term
MPLS Label Distribution
MPLS Label Distribution is the process by which routers exchange labels that tell them how to forward packets across a network without looking at the IP address each time.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.