Subnet Calculator

Calculate subnet masks, IP ranges, and network information from CIDR notation or IP/mask

What is Subnetting?

Subnetting is the practice of dividing a network into smaller sub-networks (subnets). This helps organize networks efficiently, improve security, and optimize IP address usage.

CIDR notation (Classless Inter-Domain Routing) uses a slash followed by a number to indicate how many bits are used for the network portion of the address (e.g., /24 means the first 24 bits are the network).

Key concepts:

  • Network Address: The first IP in the subnet (not assignable to hosts)
  • Broadcast Address: The last IP in the subnet (used to send to all hosts)
  • Usable IPs: IP addresses you can assign to devices (total - 2)
  • Subnet Mask: Defines which portion of IP is network vs host

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