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Subnet Mask

A 32-bit number that divides an IP address into network and host portions for routing.

NetworkingAlso called: "subnet", "network mask", "cidr"

Subnet masks define which part of an IP address represents the network and which represents individual hosts.

CIDR notation

  • /24 = 255.255.255.0 (256 addresses, 254 usable).
  • /16 = 255.255.0.0 (65,536 addresses).
  • /8 = 255.0.0.0 (16,777,216 addresses).

Subnetting benefits

  • Efficient IP address allocation.
  • Network segmentation for security and performance.
  • Isolation of broadcast domains.
  • Simplified routing and management.

Calculations

  • Network address: IP AND subnet mask.
  • Broadcast address: Last IP in the range.
  • Usable hosts: Total addresses - 2 (network + broadcast).