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300-410 Practice Question: Which TWO statements about MPLS label stack…
Which TWO statements about MPLS label stack operations in a Layer 3 VPN (L3VPN) are true? (Choose TWO.)
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
✓
A P router (core router) performs label swapping only on the top label in the label stack.
In MPLS L3VPN, the P router (core router) performs label swapping based on the top label (IGP label). The PE router (ingress) imposes two labels: the outer IGP label for transport and the inner VPN label for identifying the egress VRF. The P router does not look at the inner VPN label. Option A is correct: the P router swaps only the top label. Option B is correct: the ingress PE imposes two labels. Option C is false: the P router does not pop the VPN label; it swaps the transport label. Option D is false: the egress PE pops the VPN label, not the P router. Option E is false: the P router does not look at the VPN label; it only swaps the outer label.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
A P router (core router) performs label swapping only on the top label in the label stack.
Why this is correct
Correct. The P router swaps the outer IGP label; it does not process the inner VPN label.
- ✓
The ingress PE router imposes two labels: an outer LDP label and an inner VPN label.
Why this is correct
Correct. The outer label is for transport across the MPLS core, the inner label identifies the egress VRF.
- ✗
The P router pops the inner VPN label before forwarding the packet to the egress PE.
Why it's wrong here
Incorrect. The P router does not pop the VPN label; it only swaps the outer label.
- ✗
The egress PE router swaps the VPN label with a new label before forwarding to the CE.
Why it's wrong here
Incorrect. The egress PE pops the VPN label and forwards the IP packet to the CE.
- ✗
The P router uses the inner VPN label to make forwarding decisions.
Why it's wrong here
Incorrect. The P router only looks at the top label; the inner VPN label is transparent to it.
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
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 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.