300-410 Infrastructure Services Practice Question
A network engineer is configuring a Cisco IOS router to support MPLS Layer 3 VPNs. The engineer needs to enable the provider edge (PE) router to exchange VPNv4 routes with other PE routers. Which protocol is used to distribute VPNv4 routes between PE routers?
⚠ Common exam trap
Many candidates confuse the protocol used for label distribution (LDP) with the protocol used for VPN route distribution (MP-BGP).
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
✓
BGP with the VPNv4 address family
MP-BGP with the VPNv4 address family is the standard protocol for exchanging VPNv4 routes between PE routers in MPLS L3VPN deployments. It carries the necessary extended communities (route targets, route distinguishers) to support multiple VPNs. Other protocols like OSPF, LDP, and RSVP-TE serve different purposes and cannot distribute VPNv4 routes.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
RSVP-TE
Why it's wrong here
RSVP-TE (Resource Reservation Protocol - Traffic Engineering) is used to establish traffic-engineered label-switched paths in MPLS networks. It distributes labels for TE tunnels but does not exchange VPNv4 routes. RSVP-TE is concerned with path establishment and resource reservation, not with VPN routing information. Therefore, it is not the protocol used to distribute VPNv4 routes between PE routers.
- ✗
OSPFv2
Why it's wrong here
OSPFv2 is a link-state routing protocol used for IPv4 unicast routing within an autonomous system. It does not support the VPNv4 address family or the extended communities required for MPLS L3VPN. While OSPF can be used as the routing protocol within the MPLS core or between PE and CE routers, it cannot distribute VPNv4 routes between PE routers. Therefore, OSPFv2 is not the correct protocol for this purpose.
- ✗
LDP
Why it's wrong here
Label Distribution Protocol (LDP) is used to distribute MPLS labels for interior gateway protocol (IGP) routes within the MPLS core. It does not exchange VPNv4 routes or carry VPN-specific attributes like route targets. LDP is essential for establishing label-switched paths for the core, but it is not used for VPNv4 route distribution between PE routers. Thus, LDP is incorrect for this scenario.
- ✓
BGP with the VPNv4 address family
Why this is correct
Multiprotocol BGP (MP-BGP) with the VPNv4 address family is used to distribute VPNv4 routes between PE routers in an MPLS L3VPN environment. It carries the route targets and route distinguishers as extended communities, enabling proper VPN membership and route separation. BGP is the only protocol that supports the necessary address family and attributes for VPNv4 route exchange, making it the correct choice.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
Go deeper
Related to this question
Learn chapter
Device Management and Network Monitoring (SNMP, Syslog, NetFlow)
Key term
MP-BGP for VPN
MP-BGP for VPN is an extension of the Border Gateway Protocol that carries multiple types of network layer information to enable scalable, isolated virtual private networks over a shared provider infrastructure.
Key term
MPLS Label Distribution
MPLS Label Distribution is the process by which routers exchange labels that tell them how to forward packets across a network without looking at the IP address each time.
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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
This 300-410 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 300-410 exam.