hardMultiple ChoiceObjective-mapped
300-410 Practice Question: Which MPLS label value is reserved for the…
Which MPLS label value is reserved for the Explicit NULL label and what is its purpose?
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
✓
Label 0; used for the Explicit NULL label to indicate that the penultimate hop should pop the label.
Label value 0 is the IPv4 Explicit NULL label, used to signal the penultimate hop to pop the label stack and forward the packet based on the IP header.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Label 0; used for the Explicit NULL label to indicate that the penultimate hop should pop the label.
Why this is correct
Label 0 is the IPv4 Explicit NULL per RFC 3032.
- ✗
Label 1; used for the Router Alert label.
Why it's wrong here
Label 1 is the Router Alert label, not Explicit NULL.
- ✗
Label 2; used for the Implicit NULL label.
Why it's wrong here
Label 3 is the Implicit NULL label; label 2 is the IPv6 Explicit NULL.
- ✗
Label 3; used for the Implicit NULL label.
Why it's wrong here
Label 3 is the Implicit NULL, not Explicit NULL.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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