300-410 Layer 3 Technologies Practice Question
A network engineer is implementing MPLS Layer 3 VPN on a Cisco IOS-XE router. The engineer needs to configure the router to exchange VPNv4 routes with a route reflector. The router is already configured with BGP AS 65001 and has established an IBGP session with the route reflector. Which address family must be activated to support VPNv4 route exchange?
⚠ Common exam trap
A common mix-up: candidates confuse the IPv4 unicast address family with VPNv4; VPNv4 is a separate address family that must be explicitly activated for MPLS L3VPN route exchange.
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
✓
address-family vpnv4 unicast
MPLS L3VPN uses the VPNv4 address family to exchange labeled VPN routes between PE routers. The VPNv4 address family carries the route distinguisher and route target extended communities. Activating it under the BGP routing process on both the PE and route reflector is required. Without it, VPNv4 prefixes are not propagated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
address-family ipv6 unicast
Why it's wrong here
The IPv6 unicast address family is for native IPv6 BGP routing and does not support VPNv4 routes. It is unrelated to MPLS L3VPN for IPv4. Enabling this would not enable VPNv4 route exchange and is incorrect for the scenario.
- ✗
address-family ipv4 vrf
Why it's wrong here
The ipv4 vrf address family is used within a VRF context to configure BGP for a specific VRF, but it does not enable VPNv4 route exchange between PE routers. It is used for PE-CE routing, not for PE-PE VPNv4 route propagation. This would not achieve the goal.
- ✗
address-family ipv4 unicast
Why it's wrong here
The IPv4 unicast address family is used for standard IPv4 BGP routing, not for VPNv4. It does not carry the route distinguisher or extended communities required for MPLS L3VPN. Activating this alone will not enable VPNv4 route exchange with the route reflector.
- ✓
address-family vpnv4 unicast
Why this is correct
The VPNv4 unicast address family is specifically designed to carry MPLS L3VPN routes with route distinguishers and extended communities. Activating it under the BGP configuration enables the exchange of VPNv4 prefixes with the route reflector. This is the correct address family for MPLS L3VPN route distribution.
Go deeper
Related to this question
Learn chapter
Device Management and Network Monitoring (SNMP, Syslog, NetFlow)
Key term
BGP Route Reflector
A BGP Route Reflector is a networking device that reduces the number of BGP peer connections needed in a large network by allowing routers to share routing information without needing to connect to every other router directly.
Key term
MPLS Layer 3 VPN
A technology that uses Multiprotocol Label Switching to create secure, scalable virtual private networks that connect multiple sites at the network layer, where the service provider manages routing between customer sites.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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