350-501 MPLS and Segment Routing Practice Question
Which BGP address family must be used to exchange VPNv4 routes between PE routers in an MPLS L3VPN?
⚠ Common exam trap
Cisco often tests the distinction between the address family used for route exchange (VPNv4 unicast) versus the filtering mechanism (RT constraint), leading candidates to confuse the RT constraint address family as the primary exchange method.
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
✓
VPNv4 unicast
In an MPLS L3VPN, VPNv4 routes carry both the IPv4 prefix and the Route Distinguisher (RD) to ensure uniqueness across overlapping customer address spaces. The VPNv4 unicast address family (address-family ipv4 vpn) is the mandatory BGP address family used between PE routers to exchange these VPNv4 routes, enabling MPLS-based VPN reachability.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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RT constraint
Why it's wrong here
RT constraint is used to filter route advertisements, not to exchange VPN routes.
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IPv4 unicast
Why it's wrong here
IPv4 unicast does not carry VPN attributes like RD and RT.
- ✗
L2VPN VPLS
Why it's wrong here
L2VPN address families are for Layer 2 VPN services, not Layer 3 VPN.
- ✓
VPNv4 unicast
Why this is correct
VPNv4 unicast is the correct address family for exchanging VPN-IPv4 routes.
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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.