100-150 Question 80
Single answerA network administrator is designing a subnet plan for the IP range 192.168.10.0/24. The requirement is to create 4 subnets with an equal number of usable host addresses. Which of the following subnet masks should the administrator use, and what would be the broadcast address of the first subnet?
- A
Subnet mask: 255.255.255.192, Broadcast address: 192.168.10.63
- B
Subnet mask: 255.255.255.128, Broadcast address: 192.168.10.127
- C
Subnet mask: 255.255.255.224, Broadcast address: 192.168.10.31
- D
Subnet mask: 255.255.255.240, Broadcast address: 192.168.10.15
Show answer and explanation
Correct answer: A
Explanation
To create 4 subnets from a /24 network, you need to borrow 2 bits from the host portion of the address, resulting in a subnet mask of 255.255.255.192 (/26). This gives 2^2 = 4 subnets, each with 64 addresses (62 usable host addresses). The first subnet (192.168.10.0/26) has a broadcast address of 192.168.10.63.
- A. Correct.
Correct: A subnet mask of 255.255.255.192 (/26) divides the 192.168.10.0/24 network into 4 subnets, each with 64 addresses (including 2 reserved for network and broadcast). The broadcast address of the first subnet (192.168.10.0/26) is 192.168.10.63.
- B. Incorrect.
Incorrect: While a subnet mask of 255.255.255.128 (/25) creates 2 subnets, it does not fulfill the requirement for 4 subnets.
- C. Incorrect.
Incorrect: A subnet mask of 255.255.255.224 (/27) creates 8 subnets, but each subnet would have only 30 usable hosts, which does not meet the requirement for equal-sized subnets with the most addresses.
- D. Incorrect.
Incorrect: A subnet mask of 255.255.255.240 (/28) creates 16 subnets, but this results in too few usable hosts (14 per subnet), which is not suitable for the requirement.