Class AE Addresses

Class	Leading Bit Pattern	First Octet in Decimal	Notes
A	0xxxxxxx	0127	0 is invalid 127 reserved for loopback testing
B	10xxxxxx	128191
C	110xxxxx	192223
D	1110xxxx	224239	Reserved for multicasting
E	1111xxxx	240255	Reserved for future use/testing

Formulae

2N Where N is equal to number of bits borrowed	Number of total subnets created
2N 2	Number of valid subnets created
2H Where H is equal to number of host bits	Number of total hosts per subnet
2H 2	Number of valid hosts per subnet

Class A Address	N	H	H	H
Class B Address	N	N	H	H
Class C Address	N	N	N	H

N = Network bits

H = Host bits

All 0s in host portion = Network or subnetwork address

All 1s in host portion = Broadcast address

Combination of 1s and 0s in host portion = Valid host address