350-501 MPLS and Segment Routing Practice Question
In an MPLS L3VPN network, a customer has overlapping IP addresses between two VPNs. The provider edge routers are configured with VRF instances. Which method ensures that traffic from one VPN does not leak into the other when using MPLS labels?
⚠ Common exam trap
Cisco often tests the misconception that route distinguishers (RDs) alone provide VPN isolation, but RDs only ensure IP uniqueness in the BGP table, while route targets (RTs) are the actual mechanism for controlling route import/export between VRFs.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use distinct route targets for import and export per VRF.
Route targets (RTs) control the import and export of VPNv4 routes between VRFs on a PE router. By assigning distinct import and export RTs per VRF, the PE ensures that routes from one VPN are not installed into the routing table of another VPN, even if the customer uses overlapping IP addresses. MPLS labels are allocated per VRF forwarding instance, but the isolation is enforced by the RT-based filtering of BGP VPNv4 routes, not by label ranges or route distinguishers alone.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Assign different MPLS label ranges to each VRF.
Why it's wrong here
Label allocation is per VRF, but labels do not prevent route leaking.
- ✗
Apply BGP community strings to filter routes.
Why it's wrong here
BGP communities can be used, but route targets are the primary mechanism for VPN route distribution.
- ✓
Use distinct route targets for import and export per VRF.
Why this is correct
RTs control which routes are imported into a VRF, preventing leakage.
- ✗
Configure different route distinguishers for each VPN.
Why it's wrong here
RD makes routes unique but does not control route distribution between VRFs.
Visual reference
Go deeper
Related to this question
About these practice questions
Courseiva writes every 350-501 question from scratch — 971 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.