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300-410 Practice Question: Which THREE symptoms indicate a misconfiguration…
Which THREE symptoms indicate a misconfiguration in the MPLS L3VPN control plane between two PEs? (Choose THREE.)
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 command 'show ip bgp vpnv4 vrf CUSTOMER_A' shows no prefixes on the remote PE.
Common control plane issues include missing VPNv4 prefixes in BGP, lack of MPLS labels for VPN routes, and failure to establish the MP-BGP session. Correct routing table entries on the PE but no labels suggests a label allocation problem. Ping failure from CE to CE could be due to many issues, not specifically control plane. IGP adjacency down affects the underlay but is not a direct VPN control plane symptom.
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 command 'show ip bgp vpnv4 vrf CUSTOMER_A' shows no prefixes on the remote PE.
Why this is correct
Indicates that VPNv4 routes are not being received, a control plane issue.
- ✓
The command 'show mpls forwarding-table vrf CUSTOMER_A' shows no labels for remote prefixes.
Why this is correct
Missing labels mean the LFIB is not populated, often due to BGP label allocation failure.
- ✓
The MP-BGP session between PEs is in the 'Idle' or 'Active' state.
Why this is correct
A down MP-BGP session prevents VPN route exchange.
- ✗
Ping from CE1 to CE2 fails, but ping from CE1 to the local PE succeeds.
Why it's wrong here
This could be due to many issues (e.g., routing, MTU, label switching) and is not exclusively a control plane symptom.
- ✗
The IGP adjacency between PE and P routers is down.
Why it's wrong here
This is an underlay issue, not a direct VPN control plane problem.
Go deeper
Related to this question
Learn chapter
OSPF 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
MP-BGP for VPN
MP-BGP for VPN is an extension of the Border Gateway Protocol that carries multiple types of network layer information to enable scalable, isolated virtual private networks over a shared provider infrastructure.
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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.