350-501 Security and Services Practice Question
A service provider wants to mitigate DDoS attacks by blackholing traffic destined to a victim IP address. They plan to use Remotely Triggered Black Hole (RTBH) filtering. What BGP community is commonly used to trigger the blackhole route?
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
✓
Community 666
RTBH works by advertising a /32 route with a specific community (often 666 or a locally defined one) that causes the router to forward traffic to a null interface. The well-known community for RTBH is often 666 or custom.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Community 666
Why this is correct
Community 666 is a commonly used standard for RTBH to trigger null routing.
- ✗
Community 100
Why it's wrong here
Community 100 is not standard for RTBH.
- ✗
Community no-export
Why it's wrong here
No-export prevents route advertisement outside AS, not used for blackholing.
- ✗
Community local-AS
Why it's wrong here
Local-AS prevents advertisement to eBGP peers, not for RTBH.
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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.