mediumMultiple Choice
300-410 Practice Question: Which MPLS label is used for the Router Alert…
Which MPLS label is used for the Router Alert function, and what is its purpose?
⚠ Common exam trap
The trap is confusing the reserved MPLS labels, especially label 1 with label 0 or 3, which have different purposes.
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 1; used to alert the router to examine the packet in the control plane.
MPLS label 1 is reserved for the Router Alert Label. When a packet carries this label, it indicates that the router should examine the packet in the control plane, typically for protocols like RSVP-TE or LDP that require hop-by-hop processing. This is defined in RFC 3032.
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 1; used to alert the router to examine the packet in the control plane.
Why this is correct
Label 1 is the Router Alert label per RFC 3032.
- ✗
Label 0; used to alert the router to examine the packet.
Why it's wrong here
Label 0 is the Explicit NULL label, not Router Alert.
- ✗
Label 2; used to alert the router to examine the packet.
Why it's wrong here
Label 2 is the IPv6 Explicit NULL label.
- ✗
Label 3; used to alert the router to examine the packet.
Why it's wrong here
Label 3 is the Implicit NULL label.
Go deeper
Related to this question
Learn chapter
Control Plane Policing and Protection
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 Label Distribution
MPLS Label Distribution is the process by which routers exchange labels that tell them how to forward packets across a network without looking at the IP address each time.
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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.