mediumMultiple Choice
300-410 Practice Question: Statements about MPLS L3VPN label operations is…
Which of the following statements about MPLS L3VPN label operations is true?
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
✓
The ingress PE pushes two labels: the outer IGP label and the inner VPN label.
In MPLS L3VPN, the PE router assigns a per-VRF label (VPN label) for each prefix in the VRF. When forwarding a packet from the CE, the ingress PE pushes an IGP label (for the egress PE) and the VPN label. The egress PE pops the IGP label and uses the VPN label to identify the VRF and forward to the correct CE.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The ingress PE pushes two labels: the outer IGP label and the inner VPN label.
Why this is correct
In MPLS L3VPN, the ingress PE imposes a two-label stack: the outer label is the IGP or transport label used to reach the egress PE, while the inner VPN label identifies the destination VRF. This label stacking is the defining operation.
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The egress PE uses the IGP label to determine the VRF.
Why it's wrong here
The egress PE selects the VRF from the VPN label, not the IGP label; the IGP label only forwards the packet to the egress PE. The IGP label is tempting because it does steer traffic across the provider core, but it carries no VRF or customer context.
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The P routers swap the VPN label as they forward the packet.
Why it's wrong here
P routers swap only the outer transport label; the inner VPN label is preserved until the egress PE, which uses it to select the destination VRF. It is tempting because P routers do swap labels, but they never inspect or swap the VPN label itself.
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The ingress PE pushes only one label (the VPN label) and uses the IP destination for forwarding.
Why it's wrong here
The ingress PE pushes two labels: the outer transport (LDP) label plus the inner VPN label, and forwarding follows the outer label, not the IP destination. It is tempting because the VPN label does identify the destination VRF, but it is never the sole label pushed.
Go deeper
Related to this question
Learn chapter
MPLS L3VPN Basics
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.
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.
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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.