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This document contains table to cross reference between Subnet Mask and CIDR notation.

CIDR Length 

Mask 

# Networks

Class

# Hosts

/1

128.0.0.0

128

A

2,147,483,392

/2

192.0.0.0

64

A

1,073,741,696

/3

224.0.0.0

32

A

536,870,848

/4

240.0.0.0

16

A

268,435,424

/5

248.0.0.0

8

A

134,217,712

/6

252.0.0.0

4

A

67,108,856

/7

254.0.0.0

2

A

33,554,428

/8

255.0.0.0

1

A

16,777,214

/9

255.128.0.0

128

B

8,388,352

/10

255.192.0.0

64

B

4,194,176

/11

255.224.0.0

32

B

2,097,088

/12

255.240.0.0

16

B

1,048,544

/13

255.248.0.0

8

B

524,272

/14

255.252.0.0

4

B

262,136

/15

255.254.0.0

2

B

131,068

/16

255.255.0.0

1

B

65,024

/17

255.255.128.0

128

C

32,512

/18

255.255.192.0

64

C

16,256

/19

255.255.224.0

32

C

8,128

/20

255.255.240.0

16

C

4,064

/21

255.255.248.0

8

C

2,032

/22

255.255.252.0

4

C

1,016

/23

255.255.254.0

2

C

508

/24

255.255.255.0

1

C

254



CIDR Length 

Mask 

# Networks

# Hosts

/25

255.255.255.128

2 subnets

124

/26

255.255.255.192

4 subnets

62

/27

255.255.255.224

8 subnets

30

/28

255.255.255.240

16 subnets

14

/29

255.255.255.248

32 subnets

6

/30

255.255.255.252

64 subnets

2

/31

255.255.255.254

none

none

/32

255.255.255.255

1/256 C

1