Subnet Mask
A number that defines which portion of an IP address identifies the network vs the individual device.
A subnet mask of 255.255.255.0 (or /24 in CIDR notation) means the first 24 bits identify the network and the last 8 bits identify the host. This allows 254 usable host addresses (2^8 - 2, minus network and broadcast addresses). Subnetting divides large networks into smaller, more manageable segments for security and performance.
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