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300-410 Practice Question: Runs the following command to troubleshoot a…
A network engineer runs the following command to troubleshoot a VRF-Lite MPLS LDP issue:
R1# show mpls ldp bindings vrf CUSTOMER_F
Output: lib entry: 10.4.4.0/24, rev 2 local binding: label: 16 remote binding: lsr: 2.2.2.2:0, label: 20 lib entry: 10.5.5.0/24, rev 3 local binding: label: 17 remote binding: lsr: 2.2.2.2:0, label: 21
What does this output indicate?
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 VRF CUSTOMER_F has two prefixes with local labels 16 and 17, and remote labels 20 and 21 from LSR 2.2.2.2.
The 'show mpls ldp bindings vrf' command displays MPLS label bindings for a specific VRF. The output shows two prefixes (10.4.4.0/24 and 10.5.5.0/24) with local labels (16 and 17) and remote labels (20 and 21) from LSR 2.2.2.2. This indicates that LDP has successfully exchanged labels for these prefixes within the VRF.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
MPLS LDP has not established a session with the remote LSR 2.2.2.2.
Why it's wrong here
Remote bindings from lsr 2.2.2.2:0 are present for both prefixes, which requires an established LDP session. It is tempting when a session is suspected of being down, since absent remote bindings would indicate that, but here they are listed.
- ✓
The VRF CUSTOMER_F has two prefixes with local labels 16 and 17, and remote labels 20 and 21 from LSR 2.2.2.2.
Why this is correct
The output lists two LIB entries, 10.4.4.0/24 and 10.5.5.0/24, each with a local label (16 and 17) and a remote binding from LSR 2.2.2.2:0 using labels 20 and 21, confirming label exchange within VRF CUSTOMER_F.
- ✗
The labels are not being used because the VRF is not configured correctly.
Why it's wrong here
Both prefixes show local and remote bindings with distinct non-zero labels, proving LDP is operating correctly within the VRF. It is tempting when troubleshooting VRF-Lite, since a missing VRF-to-LDP association would produce no bindings, but here bindings exist.
- ✗
The remote LSR is using the same labels as the local router.
Why it's wrong here
Local labels 16 and 17 differ from remote labels 20 and 21, so the peers are not using identical values. It is tempting because both routers advertise labels for the same prefixes, but LDP label spaces are independently allocated per LSR.
Go deeper
Related to this question
Learn chapter
VRF-Lite and Multi-Protocol BGP
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.
Key term
MPLS Layer 3 VPN
A technology that uses Multiprotocol Label Switching to create secure, scalable virtual private networks that connect multiple sites at the network layer, where the service provider manages routing between customer sites.
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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.