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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 creates a globally unique VPNv4 prefix by combining with the IPv4 address, preventing route ambiguity.
- ✗
To control which VRFs import routes from other PEs.
Why it's wrong here
That is the function of the Route Target (RT), not the RD.
- ✗
To specify the VPN label that is used for forwarding.
Why it's wrong here
The VPN label is allocated by the LDP or BGP, not by the RD.
- ✗
To identify the VRF on the local PE router.
Why it's wrong here
The VRF is identified by its name locally; the RD is used in BGP updates.
Go deeper
Related to this question
Learn chapter
OSPF Route Summarization and Filtering
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.
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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.