200-301 Question 274
Single answerA network administrator is tasked with designing a subnet for a small branch office that requires 30 usable IP addresses. The administrator decides to use the 192.168.10.0/24 network. What subnet mask should the administrator apply to meet the requirement while minimizing wasted IP addresses?
- A
255.255.255.224
- B
255.255.255.240
- C
255.255.255.192
- D
255.255.255.248
Show answer and explanation
Correct answer: A
Explanation
The subnet mask 255.255.255.224 (or /27) allows for 32 total IP addresses, with 30 usable for hosts. This aligns exactly with the requirement while minimizing waste. Other subnet masks either fail to provide the required number of usable addresses or result in excessive unused addresses, making them unsuitable choices.
- A. Correct.
255.255.255.224 provides 32 total IP addresses, with 30 usable IP addresses after accounting for the network and broadcast addresses. This is the correct subnet mask for the requirement.
- B. Incorrect.
255.255.255.240 provides 16 total IP addresses, with only 14 usable IP addresses, which is insufficient for the requirement of 30 usable addresses.
- C. Incorrect.
255.255.255.192 provides 64 total IP addresses, with 62 usable IP addresses. While it meets the requirement, it results in wasted IP addresses and does not minimize waste.
- D. Incorrect.
255.255.255.248 provides 8 total IP addresses, with only 6 usable IP addresses, which is insufficient for the requirement of 30 usable addresses.