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Tools - Networking - CIDR

Networking Resources

CIDR Notation Quick Reference Table

This table provides a reference between the Classless Inter Domain Routing (CIDR) notation, the total number of allocated IP addresses in the notation, the decimal network mask, the network mask binary representation, and a brief description of the allocated range.

CIDR Notation

Total # Addresses

Netmask (Decimal)

Netmask (Binary)

Description

Class A

/0

4,294,967,296

0.0.0.0

00000000.00000000.00000000.00000000

Every IPv4 Address

/1

2,147,483,648

128.0.0.0

10000000.00000000.00000000.00000000

128 Class A Networks

/2

1,073,741,824

192.0.0.0

11000000.00000000.00000000.00000000

64 Class A Networks

/3

536,870,912

224.0.0.0

11100000.00000000.00000000.00000000

32 Class A Networks

/4

268,435,456

240.0.0.0

11110000.00000000.00000000.00000000

16 Class A Networks

/5

134,217,728

248.0.0.0

11111000.00000000.00000000.00000000

8 Class A Networks

/6

67,108,864

252.0.0.0

11111100.00000000.00000000.00000000

4 Class A Networks

/7

33,554,432

254.0.0.0

11111110.00000000.00000000.00000000

2 Class A Networks

/8

16,777,214

255.0.0.0

11111111.00000000.00000000.00000000

Single Class A Network

Class B

/9

8,388,608

255.128.0.0

11111111.10000000.00000000.00000000

128 Class B Networks

/10

4,194,304

255.192.0.0

11111111.11000000.00000000.00000000

64 Class B Networks

/11

2,097,152

255.224.0.0

11111111.11100000.00000000.00000000

32 Class B Networks

/12

1,048,576

255.240.0.0

11111111.11110000.00000000.00000000

16 Class B Networks

/13

524,288

255.248.0.0

11111111.11111000.00000000.00000000

8 Class B Networks

/14

262,144

255.252.0.0

11111111.11111100.00000000.00000000

4 Class B Networks

/15

131,072

255.254.0.0

11111111.11111110.00000000.00000000

2 Class B Networks

/16

65,536

255.255.0.0

11111111.11111111.00000000.00000000

Single Class B Network

Class C

/17

32,768

255.255.128.0

11111111.11111111.10000000.00000000

128 Class C Networks

/18

16,384

255.255.192.0

11111111.11111111.11000000.00000000

64 Class C Networks

/19

8,192

255.255.224.0

11111111.11111111.11100000.00000000

32 Class C Networks

/20

4,096

255.255.240.0

11111111.11111111.11110000.00000000

16 Class C Networks

/21

2,048

255.255.248.0

11111111.11111111.11111000.00000000

8 Class C Networks

/22

1,024

255.255.252.0

11111111.11111111.11111100.00000000

4 Class C Networks

/23

512

255.255.254.0

11111111.11111111.11111110.00000000

2 Class C Networks

/24

256

255.255.255.0

11111111.11111111.11111111.00000000

Single Class C Network

/25

128

255.255.255.128

11111111.11111111.11111111.10000000

126 Usable IP Addresses *

/26

64

255.255.255.192

11111111.11111111.11111111.11000000

62 Usable IP Addresses *

/27

32

255.255.255.224

11111111.11111111.11111111.11100000

30 Usable IP Addresses *

/28

16

255.255.255.240

11111111.11111111.11111111.11110000

14 Usable IP Addresses *

/29

8

255.255.255.248

11111111.11111111.11111111.11111000

6 Usable IP Addresses *

/30

4

255.255.255.252

11111111.11111111.11111111.11111100

2 usable IP Addresses *

/31

2

255.255.255.254

11111111.11111111.11111111.11111110

Unusable

/32

1

255.255.255.255

11111111.11111111.11111111.11111111

Single IP Address

 

* This subnet mask includes two additional IP addresses; a Network and Broadcast Address which are unusable by clients
 (add 2 to total count for the total allocated IP per range)