200-301 Question 273
Single answerA network administrator is tasked with summarizing the following IPv4 routes into a single prefix to reduce the size of the routing table: 192.168.0.0/25, 192.168.0.128/25, 192.168.1.0/24. Which summarized prefix would best represent these routes?
- A
192.168.0.0/22
- B
192.168.0.0/23
- C
192.168.0.0/24
- D
192.168.0.0/25
Show answer and explanation
Correct answer: B
Explanation
Route summarization aims to minimize the number of entries in the routing table by combining multiple routes into a single prefix. When summarizing, the summarized prefix must encompass all the specified routes while avoiding inclusion of unrelated IP ranges. The 192.168.0.0/23 prefix covers all the given routes (192.168.0.0/25, 192.168.0.128/25, 192.168.1.0/24) by spanning the range 192.168.0.0 to 192.168.1.255. Any broader prefix, such as /22, would unnecessarily include unrelated ranges, while narrower prefixes would fail to include all specified routes.
- A. Incorrect.
192.168.0.0/22 would include 192.168.0.0 to 192.168.3.255, which is too broad and includes IP ranges not part of the given routes.
- B. Correct.
192.168.0.0/23 is the correct answer because it includes the range 192.168.0.0 to 192.168.1.255, which covers all the given routes without including unnecessary additional IP addresses.
- C. Incorrect.
192.168.0.0/24 is too narrow and only covers 192.168.0.0 to 192.168.0.255, missing some of the specified routes.
- D. Incorrect.
192.168.0.0/25 is also too narrow and only covers 192.168.0.0 to 192.168.0.127, missing most of the specified routes.