The answer is to verify that the route target import/export values on the remote PE match those on the local PE for VRF CUSTOMER_C. This is correct because in MPLS L3VPN, VPNv4 routes are only imported into a VRF on a remote PE if the route target attached to those routes matches the VRF’s import statement; without a matching import route target on the remote PE, the routes are received in BGP but never installed into the VRF routing table, causing missing connectivity to that specific site. On the ENCOR 350-401 exam, this scenario tests your understanding of VRF route target misconfiguration as a common cause of partial reachability—a classic trap is assuming that a correctly configured local PE guarantees end-to-end connectivity, when in fact each PE must independently match route targets. Remember the mnemonic “Import to accept, export to share”: both sides must agree on the route target value for routes to flow into the VRF.
CCNP Virtualization Practice Question
This 350-401 practice question tests your understanding of virtualization. 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.
A service provider uses a Cisco ASR 1000 router to provide MPLS L3VPN services to multiple customers. Each customer has their own VRF. Recently, a new customer was added with VRF CUSTOMER_C. After configuration, the customer reports that they can reach some remote sites but not others. The network engineer checks the VRF configuration and finds that the route targets for CUSTOMER_C are correctly configured. The engineer also verifies that BGP sessions to the PE routers are up. The missing routes are from a site that uses a different PE router. Which action should the engineer take to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Verify that the route target import/export values on the remote PE match those on the local PE for VRF CUSTOMER_C.
The issue is that the remote PE router does not have the correct route target import/export configuration for VRF CUSTOMER_C. In MPLS L3VPN, VRFs on different PEs must have matching route target values to import and export VPNv4 routes into the correct VRF. Even if the local PE is correctly configured, the remote PE must also import the routes from the local PE using the same route target. Without this, the remote PE will not install the VPNv4 prefixes into its VRF, causing the customer to be unable to reach sites connected to that remote PE.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Increase the MTU on the link between the PE routers.
Why it's wrong here
MTU issues would cause packet drops, not route absence.
✗
Reconfigure LDP on the PE routers to establish a targeted session.
Why it's wrong here
LDP is not directly related to VRF route import.
✗
Check the MPLS label stack on the local PE to ensure labels are being swapped correctly.
Why it's wrong here
Label issues would affect all destinations, not just one.
✓
Verify that the route target import/export values on the remote PE match those on the local PE for VRF CUSTOMER_C.
Why this is correct
Correct: Mismatched route targets cause routes to not be imported into the VRF.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that route target configuration is only needed on one PE, or that BGP session status alone guarantees route exchange, when in fact both import and export RTs must match across all PEs participating in the same VRF.
Detailed technical explanation
How to think about this question
In MPLS L3VPN, route targets (RTs) are extended BGP communities attached to VPNv4 prefixes. The export RT on a PE tells which VPNs the route belongs to, and the import RT on another PE determines which VPNs should receive that route. If the remote PE's VRF CUSTOMER_C does not have an import RT matching the export RT of the local PE, the VPNv4 routes will not be imported into the VRF, even though BGP sessions are up and the MPLS core is functional. This is a common misconfiguration when adding new customers across multiple PEs.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the 350-401 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Virtualization — This question tests Virtualization — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Verify that the route target import/export values on the remote PE match those on the local PE for VRF CUSTOMER_C. — The issue is that the remote PE router does not have the correct route target import/export configuration for VRF CUSTOMER_C. In MPLS L3VPN, VRFs on different PEs must have matching route target values to import and export VPNv4 routes into the correct VRF. Even if the local PE is correctly configured, the remote PE must also import the routes from the local PE using the same route target. Without this, the remote PE will not install the VPNv4 prefixes into its VRF, causing the customer to be unable to reach sites connected to that remote PE.
What should I do if I get this 350-401 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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