Subnetting

Subnet Masks

Class IP Range Binary IP Range
A 255.0.0.0 11111111.00000000.00000000.00000000
B 255.255.0.0 11111111.11111111.00000000.00000000
C 255.255.255.0 11111111.11111111.11111111.00000000
Ones (1's) are network bits.
Zeros (0's) are node bits (assignable address bits).

Max. Hosts (Per Class)

Class Valid Addresses
A 16,777,216 (2^24)
B 65,536 (2^16)
C 256 (2^8)

Classless Inter Domain Routing (CIDR) Table

Bits Subnet Mask Subnets Hosts
8 255.0.0.0 1 16,777,216
16 255.255.0.0 256 65,534
24 255.255.255.0 65,536 254
25 255.255.255.128 131,072 126
26 255.255.255.192 262,144 62
27 255.255.255.224 524,288 30
28 255.255.255.240 1,048,576 14
29 255.255.255.248 2,097,152 6
30 255.255.255.252 4,194,304 2

Binary Subnet Representation

Decimal Binary Bits
.128 10000000 1
.192 11000000 2
.224 11100000 3
.240 11110000 4
.248 11111000 5
.252 11111100 6
.254 11111110 7
.255 11111111 8