350-501 Services Practice Question
A service provider deploys MPLS L3VPN to connect multiple customer sites. Which VPN address family must be enabled on the PE routers to exchange customer IPv4 routes between PEs?
⚠ Common exam trap
Cisco often tests the distinction between IPv4 unicast and VPNv4 unicast, trapping candidates who confuse standard BGP route exchange (which lacks VPN separation) with the MP-BGP VPNv4 address family required for MPLS L3VPN.
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, customer IPv4 routes must be transported between Provider Edge (PE) routers across the MPLS backbone. The VPNv4 unicast address family (AF 1, SAFI 128) is required because it carries both the IPv4 prefix and an 8-byte Route Distinguisher (RD), making routes unique across different VPNs. This address family is enabled under the BGP configuration on PE routers (e.g., `address-family vpnv4 unicast`) to exchange labeled VPN routes using MP-BGP, as defined in RFC 4364.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
VPNv4 unicast
Why this is correct
VPNv4 address family carries VPN-IPv4 routes with route distinguisher.
- ✗
IPv4 labeled-unicast
Why it's wrong here
Labeled IPv4 is for MPLS label distribution, not VPN routes.
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IPv4 unicast
Why it's wrong here
IPv4 unicast is for global routing table, not VPN routes.
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VPNv6 unicast
Why it's wrong here
VPNv6 is for IPv6 VPNs, not IPv4.
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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.