Subnet Calculator

Divides an IP network into subnetworks. Calculate information such as network + broadcast address and host range.

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Documentation

When designing networks or coming up with firewall rules, sometimes it's handy to have a subnet calculator around.  This tool helps you figure out netmasks and how many hosts can fit into a subnet.

To use this tool, just put in an IPv4 or IPv6 address and subnet mask (in CIDR notation).

For IPv4 networks, the calculator will return:
  • IP
  • Netmask
  • Wildcard mask (the inverse of the net mask)
  • CIDR notation
  • Network address
  • Usable range
  • Broadcast address
  • Number of usable hosts

For IPv6 networks, the calculator will return:
  • Expanded notation
  • Condensed notation
  • CIDR notation
  • Usable range
  • Number of usable hosts

When to use a subnet calculator
 
  • Designing a network or adding new equipment - Use the tool to help you figure out how to divide the networks and integrate new and existing network equipment.
     
  • For practice! - If you're practicing for an exam, you can use the calculator to make sure your subnet calculations are correct.
     
  • Creating/validating firewall rules - Firewalls often take in CIDR notation. CIDR notation is nice shorthand for describing a block of addresses, but isn't always the most intuitive. You can use the calculator to verify that the hosts you are allowing fall within the usable range.

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