100-150 Question 59
Single answerA network administrator is tasked with creating subnets for a company that uses the 192.168.10.0/24 network. The administrator needs at least 6 subnets with an equal number of usable host addresses in each. Which subnet mask should the administrator use?
- A
255.255.255.192
- B
255.255.255.224
- C
255.255.255.240
- D
255.255.255.248
Show answer and explanation
Correct answer: B
Explanation
To determine the correct subnet mask, the administrator must calculate how many subnets are needed and how many usable hosts are required per subnet. Using 192.168.10.0/24, the default subnet mask is 255.255.255.0. Borrowing 3 bits (resulting in a subnet mask of 255.255.255.224) provides 2^3 = 8 subnets, each with 2^5 - 2 = 30 usable hosts. This meets the requirement of at least 6 subnets and is the optimal solution.
- A. Incorrect.
255.255.255.192 provides 4 subnets with 62 usable hosts per subnet, but the administrator needs at least 6 subnets, so this option is incorrect.
- B. Correct.
255.255.255.224 provides 8 subnets with 30 usable hosts per subnet, which satisfies the requirement of at least 6 subnets. This is the correct answer.
- C. Incorrect.
255.255.255.240 provides 16 subnets, but each subnet only supports 14 usable hosts, which is not ideal if more hosts are needed. Additionally, this subnet mask provides more subnets than required.
- D. Incorrect.
255.255.255.248 provides 32 subnets, but each subnet supports only 6 usable hosts, which is too few for most practical applications in this case.