Prefix length — drag to split 32 bits into network / host
/24
Network bits (fixed)
Host bits (variable)
/24 — network
8 host bits
Subnet mask
255.255.255.0
Usable hosts
254
Network address
192.168.1.0
Broadcast address
192.168.1.255
Why usable = total − 2?
All host bits = 0 → network address (identifies the subnet, never a device).
All host bits = 1 → broadcast address (sends to every device on the subnet).