Understanding your calculation
Method, example and limitations
How the calculation works
IPv4 subnetting uses a prefix length to separate network and host bits. An address block with prefix p contains 2^(32 − p) total addresses.
Example to check
A /24 IPv4 block contains 256 total addresses. Under conventional subnet addressing, 254 are ordinary host addresses after reserving network and broadcast.
Before using the result
Special cases such as /31 and /32 do not follow the usual subtract-two rule. Routing, address reservations and IPv6 use additional rules.