Subnet / CIDR Calculator
Calculate a subnet's parameters from an IP and a prefix.
CIDR notation (for example 192.168.1.0/24) defines a subnet by indicating how many bits identify the network. This calculator gives you the network address, the broadcast address, the mask and its wildcard, the usable host range and the total number of addresses. Useful for planning networks and configuring routers.
Subnet FAQ
CIDR (Classless Inter-Domain Routing) expresses a subnet as IP/prefix, where the prefix indicates how many leading bits belong to the network. For example, /24 equals the mask 255.255.255.0 and reserves the last 8 bits for hosts.
It's the last address of the subnet and is used to send a message to all hosts on that network at once. It can't be assigned to a device, just like the network address (the first one).
Because the first address (the network) and the last (the broadcast) are reserved and can't be assigned to devices. That's why a /24 has 256 addresses but only 254 usable hosts.
They are ranges reserved for internal networks (10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16) that aren't routed on the Internet. They're used inside homes and businesses, behind a NAT router.
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