This IP subnet calculator takes an IPv4 address and a CIDR prefix and works out everything you need to understand the subnet: the network address, the broadcast address, the subnet mask, the wildcard mask, the usable host range and the number of hosts. Subnetting is a core networking skill, and CIDR notation, where a network is written as an address followed by a slash and a prefix length such as 192.168.1.0/24, is the standard way to describe it. The prefix is the number of leading bits that identify the network, so the rest identify hosts within it, and a larger prefix means a smaller subnet with fewer hosts. You enter an address and choose a prefix from /8 to /32, and the calculator masks the address to find the network, fills the host bits to find the broadcast, and counts the addresses in between. It reserves the network and broadcast addresses, so a /24 with 256 total addresses has 254 usable for devices. This is exactly what network administrators, students and home lab tinkerers need when planning address ranges, splitting a network into subnets, or configuring a router or firewall. Enter an IP address and prefix to see the full subnet breakdown straight away.
The calculator converts the address to a 32-bit number and builds the subnet mask from the prefix. The network address is the address bitwise-ANDed with the mask, and the broadcast is the network with all host bits set to 1. The usable hosts are the addresses in between, which is two fewer than the total for prefixes up to /30.
For 192.168.1.100 with a /24 prefix, the mask is 255.255.255.0, the network is 192.168.1.0 and the broadcast is 192.168.1.255. That leaves 192.168.1.1 to 192.168.1.254, which is 254 usable hosts.
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