A server administrator needs to configure a server on a network that will have no more than 30 available IP addresses. Which of the following subnet addresses will be the most efficient for this network?

A server administrator needs to configure a server on a network that will have no more than 30 available IP addresses. Which of the following subnet addresses will be the most efficient for this network?

• A. 255.255.255.224
• B. 255.255.255.0
• C. 255.255.255.128
• D. 255.255.255.192

Answer: (A)

The subnet mask 255.255.255.224, which corresponds to a CIDR notation of /27, effectively creates a subnet that allows for precisely 30 usable IP addresses. This configuration provides a total of 32 IP addresses in the subnet, but two of those addresses—one for the network and one for the broadcast—are reserved. Therefore, the actual number of usable addresses for devices is 30, which fits the requirement of the server administrator perfectly. This subnetting approach is optimal for a network that does not require more than 30 IP addresses, as it minimizes waste of IP address space. Each of the other subnet masks provided would either allocate too many addresses or not accommodate the needed addresses efficiently. For instance, with a subnet mask of 255.255.255.0, there would be 254 usable addresses, which is excessive for a network of this size. Similarly, 255.255.255.128 offers 126 usable addresses and 255.255.255.192 allows for 62 usable addresses—both options lead to unnecessary allocation of more addresses than required. The choice of a subnet mask must always consider not only the current needs but also future scalability. However, in this specific case, using

The subnet mask 255.255.255.224, which corresponds to a CIDR notation of /27, effectively creates a subnet that allows for precisely 30 usable IP addresses. This configuration provides a total of 32 IP addresses in the subnet, but two of those addresses—one for the network and one for the broadcast—are reserved. Therefore, the actual number of usable addresses for devices is 30, which fits the requirement of the server administrator perfectly.

This subnetting approach is optimal for a network that does not require more than 30 IP addresses, as it minimizes waste of IP address space. Each of the other subnet masks provided would either allocate too many addresses or not accommodate the needed addresses efficiently. For instance, with a subnet mask of 255.255.255.0, there would be 254 usable addresses, which is excessive for a network of this size. Similarly, 255.255.255.128 offers 126 usable addresses and 255.255.255.192 allows for 62 usable addresses—both options lead to unnecessary allocation of more addresses than required.

The choice of a subnet mask must always consider not only the current needs but also future scalability. However, in this specific case, using