350-501 Security and Services Practice Question
In an MPLS L3VPN, how can a service provider prevent a CE device from learning the MPLS label stack and potentially spoofing labels?
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
✓
Disable MPLS on the PE-CE interface
Disabling MPLS on the PE-CE link ensures the CE does not receive labeled packets. TTL propagation is for traceroute, not for preventing label exposure. LDP authentication secures label distribution but does not prevent CE from receiving labels if MPLS is enabled.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Disable MPLS on the PE-CE interface
Why this is correct
This prevents the CE from seeing MPLS labels.
- ✗
Use LDP authentication between PE and CE
Why it's wrong here
LDP authentication secures LDP but does not prevent label exposure.
- ✗
Configure MPLS VPN route-target filtering
Why it's wrong here
Route-target filtering controls route distribution, not label visibility.
- ✗
Enable TTL propagation on the PE-CE link
Why it's wrong here
TTL propagation does not prevent label exposure.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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