The answer is that customer routes leak into other VRFs. This occurs because route-target values control the import and export of routes between VRFs in MPLS Layer 3 VPN architectures; when these values are misconfigured in a VRF-lite setup, a VRF may incorrectly import routes from another VRF, breaking customer isolation. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this concept tests your understanding of how route-targets function as the glue between VRFs and BGP, often appearing in scenario-based questions where a misconfiguration leads to unintended route sharing. A common trap is confusing route-targets with route-distinguishers—remember that route-distinguishers make routes unique, but route-targets control the leak. Memory tip: think of route-targets as the bouncer at a club—if the bouncer has the wrong list (misconfigured import/export), the wrong customers (routes) get in.
350-501 Architecture Practice Question
This 350-501 practice question tests your understanding of architecture. 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.
In a carrier network using VRF-lite for customer isolation, which issue arises if route-target values are not correctly configured?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Customer routes leak into other VRFs.
Option B is correct because incorrect route-target configuration can cause routes from one VRF to be imported into another VRF, leading to route leakage. Option A is wrong because routes would still be installed in the VRF, but they might leak. Option C is wrong because PE-CE routing protocols are independent of route-target. Option D is wrong because BGP sessions between PEs are not directly affected by VRF route-targets.
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.
✗
Customer routes are not installed in the global table.
Why it's wrong here
Routes are installed in the VRF table, not the global table.
✗
BGP sessions between PEs flap.
Why it's wrong here
Route-target settings do not affect BGP session stability between PEs.
✗
The PE-CE routing protocol fails.
Why it's wrong here
PE-CE routing operates independently of route-target configuration.
✓
Customer routes leak into other VRFs.
Why this is correct
Mismatched route-targets can cause unintended import/export, leading to route leakage between VRFs.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 350-501 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 350-501 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Architecture — This question tests Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Customer routes leak into other VRFs. — Option B is correct because incorrect route-target configuration can cause routes from one VRF to be imported into another VRF, leading to route leakage. Option A is wrong because routes would still be installed in the VRF, but they might leak. Option C is wrong because PE-CE routing protocols are independent of route-target. Option D is wrong because BGP sessions between PEs are not directly affected by VRF route-targets.
What should I do if I get this 350-501 question wrong?
Identify which 350-501 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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