Table 1. All Possible 32 Bit Network Masks
Netmask Binary Netmask CIDR Notes

255.255.255.255

11111111.11111111.11111111.11111111

/32

Specific Host

255.255.255.254

11111111.11111111.11111111.11111110

/31

Unuseable

255.255.255.252

11111111.11111111.11111111.11111100

/30

2 useable

255.255.255.248

11111111.11111111.11111111.11111000

/29

6 useable

255.255.255.240

11111111.11111111.11111111.11110000

/28

14 useable

255.255.255.224

11111111.11111111.11111111.11100000

/27

30 useable

255.255.255.192

11111111.11111111.11111111.11000000

/26

62 useable

255.255.255.128

11111111.11111111.11111111.10000000

/25

126 useable

255.255.255.0

11111111.11111111.11111111.00000000

/24

Class C, 254 useable

255.255.254.0

11111111.11111111.11111110.00000000

/23

2 Class C’s

255.255.252.0

11111111.11111111.11111100.00000000

/22

4 Class C’s

255.255.248.0

11111111.11111111.11111000.00000000

/21

8 Class C’s

255.255.240.0

11111111.11111111.11110000.00000000

/20

16 Class C’s

255.255.224.0

11111111.11111111.11100000.00000000

/19

32 Class C’s

255.255.192.0

11111111.11111111.11000000.00000000

/18

64 Class C’s

255.255.128.0

11111111.11111111.10000000.00000000

/17

128 Class C’s

255.255.0.0

11111111.11111111.00000000.00000000

/16

Class B

255.254.0.0

11111111.11111110.00000000.00000000

/15

2 Class B’s

255.252.0.0

11111111.11111100.00000000.00000000

/14

4 Class B’s

255.248.0.0

11111111.11111000.00000000.00000000

/13

8 Class B’s

255.240.0.0

11111111.11110000.00000000.00000000

/12

16 Class B’s

255.224.0.0

11111111.11100000.00000000.00000000

/11

32 Class B’s

255.192.0.0

11111111.11000000.00000000.00000000

/10

64 Class B’s

255.128.0.0

11111111.10000000.00000000.00000000

/9

128 Class B’s

255.0.0.0

11111111.00000000.00000000.00000000

/8

Class A

254.0.0.0

11111110.00000000.00000000.00000000

/7

252.0.0.0

11111100.00000000.00000000.00000000

/6

248.0.0.0

11111000.00000000.00000000.00000000

/5

240.0.0.0

11110000.00000000.00000000.00000000

/4

224.0.0.0

11100000.00000000.00000000.00000000

/3

192.0.0.0

11000000.00000000.00000000.00000000

/2

128.0.0.0

10000000.00000000.00000000.00000000

/1

0.0.0.0

00000000.00000000.00000000.00000000

/0

Entire IP space

Table 2. Private IP Space

RFC1918 name

IP address range

number of addresses

classful description

largest CIDR block (subnet mask)

host id size

24-bit block

10.0.0.0 - 10.255.255.255

16,777,216

single class A

10.0.0.0/8 (255.0.0.0)

24 bits

20-bit block

172.16.0.0 - 172.31.255.255

1,048,576

16 contiguous class Bs

172.16.0.0/12 (255.240.0.0)

20 bits

16-bit block

192.168.0.0 - 192.168.255.255

65,536

256 contiguous class Cs

192.168.0.0/16 (255.255.0.0)

16 bits

ipcalc

Another way to solve these problems is to use ipcalc which is a bona fide awesome tool. apt-get install ipcalc