350-501 Security and Services Practice Question
Which MPLS security best practice helps prevent label spoofing attacks where an attacker injects MPLS packets with a forged label stack to bypass ACLs?
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
✓
Disabling TTL propagation on PE-CE interfaces
None of the provided options are the direct best practice to prevent label spoofing. The primary Cisco-recommended method is to disable MPLS on PE-CE interfaces or apply inbound label filtering to reject labeled packets from untrusted sources.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Disabling TTL propagation on PE-CE interfaces
Why this is correct
Disabling TTL propagation is a security measure for hiding network topology, but it does not prevent label spoofing directly.
- ✗
Enabling MPLS on all interfaces including CE-facing
Why it's wrong here
Enabling MPLS on CE-facing interfaces would allow untrusted sources to inject labeled packets, increasing the risk of label spoofing.
- ✗
Enabling TTL propagation on all PE routers
Why it's wrong here
Enabling TTL propagation exposes network topology and does not prevent label spoofing.
- ✗
Using IP explicit null labels on all LSPs
Why it's wrong here
Using IP explicit null labels is used for other purposes like preventing PHP or preserving QoS, not for preventing label spoofing.
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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.