350-501 Architecture Practice Question
Exhibit
PE1#show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or Tunnel Id Switched interface 16 Pop Label 10.0.0.0/8 0 Gi0/0/0 192.168.1.1 17 34 10.0.1.0/24 0 Gi0/0/1 192.168.1.2 18 Untagged 10.0.2.0/24 0 Gi0/0/2 192.168.1.3
Refer to the exhibit. What is the significance of the entry with 'Pop Label'?
⚠ Common exam trap
Cisco often tests the distinction between 'Pop Label' (PHP) and a generic label removal at the egress router, tricking candidates into thinking any label pop is the same as PHP, when in fact PHP specifically occurs at the penultimate hop.
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
✓
It indicates the penultimate hop popping (PHP)
In MPLS, the 'Pop Label' entry in a forwarding table indicates the Penultimate Hop Popping (PHP) operation. PHP is a standard behavior (RFC 3031) where the penultimate router removes the MPLS label before forwarding the packet to the egress LSR, reducing the egress router's processing load. This is explicitly signaled via the 'implicit-null' label (label value 3) in LDP or RSVP-TE.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
It indicates a merge operation
Why it's wrong here
Merge is not indicated by Pop Label.
- ✓
It indicates the penultimate hop popping (PHP)
Why this is correct
PHP removes the label before sending to the egress.
- ✗
It indicates the label is removed at this router
Why it's wrong here
Actually the label is popped before forwarding, so it is removed here, but the term PHP is more precise. However, technically it is removed, but the best answer is PHP.
- ✗
It indicates an error
Why it's wrong here
Pop Label is normal in PHP.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-501 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 350-501 exam.