Quick Answer
The answer is VRF-Lite, the correct mechanism for ensuring PE customer isolation in an MPLS L3VPN design. VRF-Lite allows a single provider edge router to maintain multiple independent routing tables, each dedicated to a specific customer, so routing updates for one customer never interfere with another. This isolation is achieved without MPLS, relying solely on IP forwarding and per-VRF routing instances, making it ideal for scenarios where full MPLS signaling is unnecessary. On the Cisco SPCOR / CCNP Service Provider Core 350-501 exam, this concept tests your understanding of Layer 3 VPN fundamentals and the distinction between VRF-Lite and full MPLS VPNs—a common trap is assuming MPLS is always required for isolation. Remember, VRF-Lite is the lightweight, table-only approach: think “VRF = Virtual Routing Forwarding, Lite = no MPLS label overhead.” A useful memory tip is “Lite keeps it local,” meaning routing stays within the PE without label distribution.
This 350-501 practice question tests your understanding of architecture. 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 solution and must ensure that the provider edge (PE) routers can handle routing updates for multiple customers without interfering with each other. Which mechanism should be used on the PE routers?
Route distinguishers
Why wrong: Route distinguishers make overlapping prefixes unique but do not provide separate tables.
Route reflectors
Why wrong: Route reflectors reduce BGP peering but do not isolate routing tables.
MPLS-TE
Why wrong: MPLS-TE is for traffic engineering, not routing isolation.
VRF-Lite
VRF-Lite creates separate routing tables for each customer.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
VRF-Lite
VRF-Lite (Virtual Routing and Forwarding) is the correct mechanism because it allows a single PE router to maintain multiple separate routing tables (VRFs), each dedicated to a different customer. This ensures that routing updates for one customer are isolated from another, preventing interference. VRF-Lite achieves this without MPLS, using only IP forwarding and per-VRF routing instances.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Route distinguishers
Why it's wrong here
Route distinguishers make overlapping prefixes unique but do not provide separate tables.
Route reflectors
Why it's wrong here
Route reflectors reduce BGP peering but do not isolate routing tables.
MPLS-TE
Why it's wrong here
MPLS-TE is for traffic engineering, not routing isolation.
VRF-Lite
Why this is correct
VRF-Lite creates separate routing tables for each customer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Cisco often tests the distinction between VRF-Lite (which provides routing isolation without MPLS) and full MPLS L3VPN (which uses RDs and route targets for VPNv4 prefix uniqueness and distribution), leading candidates to mistakenly choose route distinguishers as the isolation mechanism.
Detailed technical explanation
VRF-Lite implements per-VRF routing tables using separate RIBs and FIBs, each with its own set of interfaces and routing protocols. In a real-world scenario, a PE router might run OSPF in one VRF for a customer and EIGRP in another, with no route leakage between them. This is achieved by associating each interface with a specific VRF using the 'ip vrf forwarding' command, and the router maintains separate CEF tables per VRF.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Architecture — This question tests Architecture — Read the scenario before looking for a memorised answer..
The correct answer is: VRF-Lite — VRF-Lite (Virtual Routing and Forwarding) is the correct mechanism because it allows a single PE router to maintain multiple separate routing tables (VRFs), each dedicated to a different customer. This ensures that routing updates for one customer are isolated from another, preventing interference. VRF-Lite achieves this without MPLS, using only IP forwarding and per-VRF routing instances.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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.
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