easyMultiple Choice
300-410 Practice Question: In MPLS L3VPN, what is the purpose of the Route…
In MPLS L3VPN, what is the purpose of the Route Distinguisher (RD)?
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
✓
To make IPv4 prefixes unique across different VRFs in the MPLS network.
The RD is an 8-byte value prepended to an IPv4 prefix to create a unique VPNv4 prefix. This allows overlapping IPv4 addresses from different VRFs to be carried in the same BGP table without conflict.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
To make IPv4 prefixes unique across different VRFs in the MPLS network.
Why this is correct
The RD prepends an 8-byte value to the IPv4 prefix, forming a VPNv4 address. This guarantees uniqueness across VRFs even when different tenants use identical IPv4 ranges, satisfying the constraint that overlapping customer prefixes must remain distinguishable within the MPLS L3VPN.
- ✗
To control which VRFs import routes from other PEs.
Why it's wrong here
Import control is performed by route targets, which determine VRF import and export policy. The RD only makes prefixes unique across VRFs by prepending an identifier, so identical addresses from different customers can coexist in MP-BGP. Route targets would be correct when engineering which VRFs share routes.
- ✗
To specify the VPN label that is used for forwarding.
Why it's wrong here
The VPN label is assigned per route by the egress PE and distributed through MP-BGP, not derived from the RD. The RD merely prefixes the IPv4 address to create a unique VPNv4 prefix. It would be relevant when distinguishing overlapping customer address space, not when specifying forwarding labels.
- ✗
To identify the VRF on the local PE router.
Why it's wrong here
The local VRF is identified by the route target and the VRF's own route table, not by the RD. The RD only ensures globally unique VPNv4 prefixes in MP-BGP. It would be the right concept when two customers use the same address range and need separate entries.
Go deeper
Related to this question
Learn chapter
MPLS L3VPN Basics
Key term
LDP Protocol
LDP, or Label Distribution Protocol, is a protocol that routers use to automatically exchange labels that enable MPLS (Multiprotocol Label Switching) to create fast, efficient paths for data packets across a network.
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.
About these practice questions
This 300-410 question is part of Courseiva's 1,401-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam 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 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.