In computer networking, what does a subnet mask do?

A subnet mask is a key component in IP networking that defines the range of IP addresses available within a specific subnet or network segment. It helps to separate the network portion of an IP address from the host portion, allowing a device to determine which part of the address refers to the network itself and which part can be allocated to individual devices or hosts on that network.

By using a subnet mask, a device can effectively make decisions about whether an IP address is part of its local network or if it needs to send data to a different network. This is essential for managing IP addresses efficiently and maintaining organized and functional network architecture. For example, if a device has the IP address 192.168.1.1 with a subnet mask of 255.255.255.0, it understands that the first three octets (192.168.1) represent the network, and the last octet indicates a specific host within that network.

The other options do not accurately describe the function of a subnet mask. Identifying MAC addresses pertains to the data link layer and involves physical addressing, while routing packets involves the role of routers and routing protocols. Encrypting data for secure transmission is related to data security and is not a function of a subnet mask