350-501 Networking Practice Question
A customer reports intermittent packet loss on a MPLS L3VPN connection. The PE router shows 'show mpls forwarding' entries for the CE prefix, but ping from the PE to the CE fails intermittently. Which action should be taken to isolate the issue?
⚠ Common exam trap
Cisco often tests the distinction between control-plane verification (routing table, BGP) and data-plane verification (MPLS forwarding, LSP) in MPLS L3VPN troubleshooting, leading candidates to mistakenly focus on label operations or LSPs when the root cause is a missing or unstable route.
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
✓
Check 'show ip route vrf CUSTOMER' and 'show bgp vpnv4 unicast vrf CUSTOMER' to confirm the VRF routes.
The intermittent packet loss suggests a control-plane issue rather than a data-plane problem. By checking 'show ip route vrf CUSTOMER' and 'show bgp vpnv4 unicast vrf CUSTOMER', you can verify that the VRF route for the CE prefix is present in the routing table and that BGP is advertising the correct VPNv4 route with the proper next-hop and label. This isolates whether the failure is due to missing or incorrect route propagation, which is a common cause of intermittent reachability in MPLS L3VPN.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Check 'show ip route vrf CUSTOMER' and 'show bgp vpnv4 unicast vrf CUSTOMER' to confirm the VRF routes.
Why this is correct
This verifies that the VRF has the correct routes and that BGP VPNv4 routes are properly imported.
- ✗
Use 'show mpls lsp' to verify the LSP to the CE's PE.
Why it's wrong here
LSP status is for the MPLS path, but the issue may be VRF-related.
- ✗
Examine the 'show mpls forwarding vrf CUSTOMER' output to see label operations.
Why it's wrong here
This shows label operations but does not isolate VRF route import issues.
- ✗
Review the 'show bgp vpnv4 unicast all' output to verify route advertisement.
Why it's wrong here
The issue is with MPLS forwarding, not BGP advertisement.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.