What does a subnet mask identify?

A subnet mask is a fundamental component in networking that helps determine the range of valid IP addresses within a particular network segment. It effectively splits the IP address into two parts: the network portion and the host portion. The network portion, indicated by the subnet mask, defines which part of the IP address refers to the network itself and which part can be used for assigning addresses to devices (hosts) within that network.

For instance, in an IP address such as 192.168.1.1 with a subnet mask of 255.255.255.0, the subnet mask identifies that the first three octets (192.168.1) represent the network, while the last octet can be assigned to individual devices (0-255) in that network. This means there can be 256 possible IP addresses (0-255), with certain addresses reserved for network identification and broadcasts.

The other options do not accurately describe the function of a subnet mask. Data transfer speed is not relevant to the subnet mask as it pertains to bandwidth and connection quality, whereas network topology refers to the layout of the network structure (physical or logical arrangement) and maximum number of devices is typically governed by the design of the network and its addressing structure rather than solely