Subnet Mask
A number that defines which portion of an IP address identifies the network vs the host.
A subnet mask like 255.255.255.0 (or /24 in CIDR notation) means the first 24 bits identify the network and the last 8 bits identify individual devices. This allows 254 usable host addresses (2^8 - 2 for network and broadcast addresses). Subnetting divides large networks into smaller segments for security, performance, and organization. Common masks: /24 (254 hosts), /16 (65,534 hosts), /8 (16 million hosts). Understanding subnets is essential for network administration and cloud infrastructure.