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300-410 Practice Question: Which TWO statements about MPLS label imposition,…
Which TWO statements about MPLS label imposition, disposition, and swapping are true? (Choose TWO.)
⚠ Common exam trap
The trap is confusing the roles of ingress, intermediate, and egress LSRs, and assuming PHP requires explicit configuration when it is actually enabled by default.
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
✓
Penultimate Hop Popping (PHP) reduces the processing load on the egress LSR by having the penultimate LSR pop the label.
Option A is correct because Penultimate Hop Popping (PHP) lets the penultimate LSR pop the MPLS label before forwarding the packet to the egress LSR, so the egress LSR receives a plain IP packet and avoids an extra label lookup, reducing its processing load. Option B is correct because a core/intermediate LSR performs the label swap operation, replacing the incoming label value with the outgoing label value from its LFIB (LIB) entry before forwarding the frame. Option C is wrong because label imposition (push) is performed by the ingress LSR (ingress edge LER), not the egress LSR, which performs disposition (pop) or receives an already-popped packet. Option D is wrong because PHP is a normal behavior between adjacent LSRs and does not require the egress LSR to be non-adjacent to the penultimate LSR. Option E is wrong because PHP is enabled by default on Cisco IOS routers (the implicit null label is advertised), not disabled by default requiring explicit configuration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Penultimate Hop Popping (PHP) reduces the processing load on the egress LSR by having the penultimate LSR pop the label.
Why this is correct
PHP offloads the egress LSR: the penultimate router pops the transport label so the egress receives an unlabelled packet and performs a single IP lookup instead of a label lookup followed by an IP lookup, reducing its forwarding burden.
- ✓
An intermediate LSR performs a label swap operation: it replaces the incoming label with an outgoing label.
Why this is correct
A label swap occurs at intermediate LSRs: the router looks up the incoming label in its LFIB and rewrites it with the corresponding outgoing label before forwarding. This preserves the label-switched path across the MPLS core without imposing or removing labels.
- ✗
The egress LSR performs label imposition (push) before forwarding the IP packet to the destination.
Why it's wrong here
Label imposition occurs at the ingress LSR, which pushes the label onto the unlabelled IP packet entering the MPLS domain. The egress LSR instead performs disposition, removing the label before delivering the packet. Imposition is tempting because it is the first label operation in the forwarding path, but it belongs to ingress, not egress.
- ✗
PHP is enabled only when the egress LSR is not directly connected to the penultimate LSR.
Why it's wrong here
PHP operates regardless of whether the egress LSR is directly connected to the penultimate LSR; adjacency is not the trigger. The penultimate LSR pops the label whenever it has an implicit-null label for the destination. Direct connectivity is tempting because it affects label distribution method, not PHP activation.
- ✗
By default, PHP is disabled on Cisco IOS routers and must be explicitly configured.
Why it's wrong here
PHP is enabled by default on Cisco IOS routers; the penultimate LSR pops the outer label so the egress LSR receives an unlabelled packet. Disabling it requires explicit configuration, not enabling. The statement inverts the default, which is tempting because PHP behaviour is configurable and often discussed alongside explicit-null settings.
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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.