With CIDR (Common Internet Domain Routing), the first decimal number isn't important any more. The /24 netmask means that there's one octet (256) numbers that aren't part of the network number. The .0 address is the network number itself and .255 is the broadcast address of the network, so that leaves 254 available node numbers, but one of those has to be a router or else the machines can't communicate with other networks.
