350-501 Security and Services Practice Question
An SP detects a volumetric DDoS attack targeting a customer network. The SP uses Cisco's S/RTBH technique to drop attack traffic. Which action is performed by the edge routers upon receiving a BGP route with a specific community?
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
✓
The edge router installs a /32 route pointing to a discard interface
S/RTBH works by advertising a /32 prefix (the victim's IP) with a special BGP community (e.g., NO_EXPORT) and a next-hop of the discard interface (e.g., Null0). Edge routers install the route pointing to Null0, dropping traffic to that IP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The edge router applies a BGP FlowSpec rule to rate-limit the traffic
Why it's wrong here
FlowSpec can filter or rate-limit, but S/RTBH specifically uses a /32 null route.
- ✗
The edge router forwards the attack traffic to a scrubbing center
Why it's wrong here
That is DDoS diversion, not S/RTBH.
- ✓
The edge router installs a /32 route pointing to a discard interface
Why this is correct
The /32 route with next-hop Null0 causes traffic to be dropped.
- ✗
The edge router sends ICMP unreachable messages to the attacker
Why it's wrong here
S/RTBH drops traffic silently; ICMP unreachable is not generated.
Go deeper
Related to this question
About these practice questions
One of 971 original 350-501 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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.