hardMultiple Select
300-410 Practice Question: Which THREE statements about MPLS label…
Which THREE statements about MPLS label operations (push, swap, pop) are true? (Choose THREE.)
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 LSR performs a label push operation.
In MPLS, the ingress LSR pushes a label, transit LSRs swap labels, and the penultimate hop router (PHP) pops the label. The egress LSR does not perform label operations if PHP is used. Label operations are based on the label forwarding table, not the routing table directly.
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 LSR performs a label push operation.
Why this is correct
The ingress label edge router classifies the incoming packet, consults the FEC-to-NHLFE mapping and imposes the label stack before forwarding into the MPLS domain. Pushing is therefore the ingress LSR's defining operation, adding the label header the core will act upon.
- ✓
The transit LSR performs a label swap operation.
Why this is correct
A transit label switch router receives a labelled packet, looks up the incoming label in its LFIB and replaces it with the outgoing label for the next hop. Swapping preserves the stack depth while remapping the label value, which is the core's forwarding behaviour.
- ✗
The egress LSR always performs a label pop operation.
Why it's wrong here
The egress LSR pops only when it is the penultimate hop or the destination; otherwise it swaps or pushes. It is tempting because PHP makes popping at the edge common, so it is the correct description when the egress LSR is directly attached to the destination network.
- ✓
The penultimate hop router (PHP) performs a label pop operation.
Why this is correct
The penultimate hop router removes the transport label before forwarding to the egress LSR, so the final router receives an unlabelled packet and avoids a second lookup. This implicit null behaviour is the pop operation performed at the penultimate hop.
- ✗
Label operations are determined by the IP routing table.
Why it's wrong here
Label operations follow the incoming label and LFIB, not the IP routing table; the IP table selects the FEC and next hop before labels apply. It is tempting because IP routing does drive forwarding decisions, so it is the correct reference when troubleshooting unlabelled IP transit across an MPLS domain.
Go deeper
Related to this question
Learn chapter
ACL-Based Traffic Filtering and Policy-Based Routing
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.