Which subnet mask allows for the most number of hosts within a subnet?

The subnet mask 255.255.255.0, also known as a /24 subnet, provides the highest number of usable host addresses within a single subnet among the given options. This subnet mask divides the IP address into two parts: the network portion and the host portion.

With a /24 subnet, there are 8 bits available for host addresses (since there are 32 bits in total in an IPv4 address). This allows for 2^8, which equals 256 total addresses within the subnet. However, two addresses are reserved: one for the network address and another for the broadcast address. This means that there are 254 usable addresses for hosts.

In contrast, the other subnet masks listed—255.255.255.128 (/25), 255.255.255.192 (/26), and 255.255.255.224 (/27)—reduce the number of host bits, resulting in fewer usable addresses. Specifically, each of these masks corresponds to progressively fewer available host addresses due to the higher number of bits allocated for the network portion.

Thus, the 255.255.255.0 subnet mask offers the best balance for accommodating the most hosts within a subnet.