IPv4 subnetting and CIDR
An IPv4 address and a slash with a number, like /26, hide a full binary calculation. Before splitting a network into smaller blocks, it is worth closing that calculation once with concrete numbers to see exactly what the prefix decides.
6 host bits give 2 to the 6th power, 64 addresses; subtracting the network and broadcast addresses leaves 62, the standard math for any prefix between /1 and /30.
A prefix meant for the link between two routers, with no room, and no need, to waste 2 of the 4 addresses a traditional /30 would use.
With no host bits left over, the block describes a single address, the pattern used to identify a router loopback interface.
Yes. It helps visualize the main subnetting outputs for both IPv4 and IPv6, including split scenarios and more detailed planning workflows.
Because the first address in the block identifies the network itself and the last is reserved for broadcast; neither can be assigned to a device, leaving 2 to the power of host bits minus 2.
A /24 has 8 host bits, 256 addresses and 254 usable. A /26 has 6 host bits, 64 addresses and 62 usable: the same /24 block split into 4 equal /26 subnets.
No. RFC 1918 reserves only 172.16.0.0 through 172.31.255.255, a /12 block. Addresses like 172.32.0.1 or 172.64.0.1 fall outside that range and are public.
Because RFC 3021 carves out a specific exception for point-to-point links between two routers: with only 2 possible addresses, reserving one for network and one for broadcast would leave the link with zero usable addresses, so both count instead.
All calculations run locally in your browser. Nothing is sent to the network or to external services.