The answer is `show mpls forwarding-table vrf CUSTOMER_A`, along with `show ip route vrf <vrf>` and `show ip bgp vpnv4 vrf <vrf>`. These three commands form the essential triad for MPLS L3VPN troubleshooting because they verify the complete data path: the VRF routing table confirms the remote CE prefix is installed, the BGP VPNv4 table ensures the route was received and processed by the PE, and the MPLS forwarding table checks that a valid label entry exists for that prefix, which is critical for label-switched forwarding across the provider core. On the Cisco CCNP ENARSI 300-410 exam, this question tests your ability to isolate whether the issue lies in the control plane (routing/BGP) or the data plane (label switching). A common trap is to jump to `show mpls ldp neighbor` or `ping vrf` first, but those verify the underlay or end-to-end connectivity, not the presence of the VPN route itself. Memory tip: think "Route, BGP, Label" — if all three show the remote prefix, the problem is likely elsewhere, such as MTU or the CE’s own routing.
300-410 MPLS L3VPN Practice Question
This 300-410 practice question tests your understanding of mpls l3vpn. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Which THREE commands would a network engineer use to troubleshoot an MPLS L3VPN issue where a CE router cannot reach a remote CE? (Choose THREE.)
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
show ip route vrf CUSTOMER_A
Troubleshooting end-to-end connectivity involves checking the VRF routing table, the BGP VPNv4 table, and the MPLS forwarding table. 'show ip route vrf <vrf>' verifies that the remote prefix is present. 'show ip bgp vpnv4 vrf <vrf>' confirms BGP has the route. 'show mpls forwarding-table vrf <vrf>' checks for label entries. 'ping vrf' tests connectivity from the PE. 'show mpls ldp neighbor' checks LDP status, which is important for the underlay but not directly for VPN route presence.
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.
✓
show ip route vrf CUSTOMER_A
Why this is correct
Checks if the remote CE prefix is in the VRF routing table.
This tests connectivity but does not provide diagnostic information about why it fails.
✗
show mpls ldp neighbor
Why it's wrong here
Checks LDP neighbor status, which is an underlay issue; not specific to VPN route troubleshooting.
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 L3VPN — This question tests MPLS L3VPN — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: show ip route vrf CUSTOMER_A — Troubleshooting end-to-end connectivity involves checking the VRF routing table, the BGP VPNv4 table, and the MPLS forwarding table. 'show ip route vrf <vrf>' verifies that the remote prefix is present. 'show ip bgp vpnv4 vrf <vrf>' confirms BGP has the route. 'show mpls forwarding-table vrf <vrf>' checks for label entries. 'ping vrf' tests connectivity from the PE. 'show mpls ldp neighbor' checks LDP status, which is important for the underlay but not directly for VPN route presence.
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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