The answer is to use a separate VRF per site with a unique route distinguisher (RD). This works because each VRF maintains an isolated routing table, and the RD prepended to each IPv4 prefix creates a unique 96-bit VPNv4 address, allowing the MPLS L3VPN backbone to distinguish between overlapping IP addresses from different sites. On the Cisco SPCOR 350-501 exam, this concept tests your understanding of how VRFs and RDs solve the fundamental challenge of customer address overlap without requiring NAT or renumbering. A common trap is confusing the RD with the route target (RT); remember that the RD ensures uniqueness inside the MPLS core, while the RT controls route distribution between VRFs. For a memory tip, think of the RD as a “name tag” that makes each duplicate IP address globally unique within the provider’s network.
350-501 Networking Practice Question
This 350-501 practice question tests your understanding of networking. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
An engineer is designing an MPLS L3VPN for a customer with multiple sites. The customer requires overlapping IP addresses between sites. Which method allows the provider to support overlapping customer addresses?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use separate VRF per site with route distinguisher.
B is correct because a separate VRF per site with a unique route distinguisher (RD) allows the provider to maintain isolated routing tables for each customer site. This isolation enables overlapping IP addresses between sites, as each VRF treats its prefixes as unique within the MPLS L3VPN backbone, regardless of address duplication.
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.
✗
Implement VPLS instead of L3VPN.
Why it's wrong here
VPLS is a Layer 2 VPN, not a Layer 3 solution for overlapping addressing.
✓
Use separate VRF per site with route distinguisher.
Why this is correct
Each VRF has its own routing table, and the RD makes routes globally unique even with overlapping IPs.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use BGP communities to control route distribution.
Why it's wrong here
Communities influence routing policy but do not prevent address overlap.
✗
Use the same VRF for all sites with different route targets.
Why it's wrong here
Same VRF would merge routes, causing address conflicts.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that route targets alone solve overlapping address issues, but the trap here is that route targets control route propagation, not address uniqueness—only the route distinguisher (RD) within a VRF provides the necessary prefix uniqueness.
Detailed technical explanation
How to think about this question
In MPLS L3VPN, each VRF is associated with a unique RD (e.g., 65000:1) to make overlapping customer prefixes globally unique within the MPLS backbone. The provider edge (PE) router uses the RD to distinguish between identical IP addresses from different VRFs, and route targets (RTs) control which VRFs import/export routes, enabling site-specific route distribution without address collision.
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 350-501 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Networking — This question tests Networking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use separate VRF per site with route distinguisher. — B is correct because a separate VRF per site with a unique route distinguisher (RD) allows the provider to maintain isolated routing tables for each customer site. This isolation enables overlapping IP addresses between sites, as each VRF treats its prefixes as unique within the MPLS L3VPN backbone, regardless of address duplication.
What should I do if I get this 350-501 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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