Cisco
200-101 · Question #118
200-101 Question #118: Real Exam Question with Answer & Explanation
The correct answer is B: 10.0.0.0 /22. Route summarization finds the shortest prefix covering all specific networks; four consecutive /24 subnets share a /22 boundary, making /22 the tightest valid summary.
Question
Refer to the exhibit. What is the most appropriate summarization for these routes?
Options
- A10.0.0.0 /21
- B10.0.0.0 /22
- C10.0.0.0 /23
- D10.0.0.0 /24
Explanation
Route summarization finds the shortest prefix covering all specific networks; four consecutive /24 subnets share a /22 boundary, making /22 the tightest valid summary.
Common mistakes.
- A. A /21 summary covers eight /24 subnets (10.0.0.0 through 10.0.7.255), which over-summarizes and advertises address space not present in the exhibit.
- C. A /23 summary covers only two /24 subnets (10.0.0.0 and 10.0.1.0), which under-summarizes and fails to include all routes shown.
- D. A /24 represents a single subnet and provides no summarization benefit; it does not consolidate multiple routes into one advertisement.
Concept tested. CIDR route summarization supernetting calculation
Reference. https://www.cisco.com/c/en/us/support/docs/ip/ip-routing/13811-16.html
Community Discussion
No community discussion yet for this question.