350-501 Security and Services Practice Question
During a DDoS attack, an SP uses Cisco Peakflow for detection and wants to drop attack traffic at the edge routers. They decide to use S/RTBH. Which action must be performed on the edge routers to trigger the black hole?
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
✓
Advertise the victim's IP via BGP with a blackhole community to edge routers
Remotely Triggered Black Hole (RTBH) works by advertising a /32 route for the victim's IP address with a specific BGP community (e.g., NO_EXPORT) to a black hole next-hop (e.g., 192.0.2.1). The edge routers must be configured to trigger based on that community.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use BGP Flowspec to create a rule that drops traffic to the victim
Why it's wrong here
BGP Flowspec operates by distributing fine-grained n-tuple matching rules to drop specific traffic types, whereas S/RTBH relies on a Next Hop attribute change to discard all traffic destined for a specific IP. While BGP Flowspec is the correct mechanism when an operator needs to filter specific protocols or source ports rather than discarding all traffic to a victim, it does not facilitate the remote trigger black hole mechanism required by this scenario.
- ✓
Advertise the victim's IP via BGP with a blackhole community to edge routers
Why this is correct
This is the standard RTBH mechanism: trigger routers to install a null route for the victim's IP.
- ✗
Configure a static null route and redistribute into IGP
Why it's wrong here
RTBH uses BGP, not IGP redistribution.
- ✗
Deploy IDMS traffic scrubbing inline
Why it's wrong here
IDMS scrubs traffic, but S/RTBH is a different mechanism.
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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.