IP Addressing Guide

 

Class A first octet range 1 127* (Network 127 is reserved for loopback and internal testing) Leading bit pattern 0

Class B first octet range 128 191 Leading bit pattern 10

Class C first octet range 192 223 Leading bit pattern 110

Class D first octet range 224 239 (Reserved for multicast) Leading bit pattern 1110

Class E first octet range 240 255 (Reserved for experimental, used for research) Leading bit pattern 11110

 

Maximum number of unique addresses in each class

Class A 27 2 = 126 Class B 214 2 = 16,382 Class C 221 2 = 2,097,150

Formulas to determine the number of subnets or hosts created by borrowing from the host portion of the address

M = the number of bits borrowed (Masked) U = the number of bits remaining or not borrowed (Unmasked)

2M = Total # of subnets created 2U = Total # of host on each subnets

2M 2 = Useable # of subnet created 2U 2 = Useable # of host on each subnet

Class A License

N.H.H.H

 

 

 

 

Class B License

N.N.H.H

 

 

 

# of Bits Borrowed

Subnet Mask

Total # Subnets

Useable # Subnets

Total # Hosts

Useable # Hosts

# of Bits Borrowed

Subnet Mask

Total # Subnets

Useable # Subnets

Total # Hosts

Useable # Hosts

2

255.192.0.0

4

2

4,194,304

4,194,302

 

2

255.255.192.0

4

2

16,384

16,382

3

255.224.0.0

8

6

2,097,152

2,097,150

 

3

255.255.224.0

8

6

8,192

8,190

4

255.240.0.0

16

14

1,048,576

1,048,574

 

4

255.255.240.0

16

14

4,096

4,094

5

255.248.0.0

32

30

524,288

524,286

 

5

255.255.248.0

32

30

2,048

2,046

6

255.252.0.0

64

62

262,144

262,142

 

6

255.255.252.0

64

62

1,024

1,022

7

255.254.0.0

128

126

131,072

131,070

 

7

255.255.254.0

128

126

512

510

8

255.255.0.0

256

254

65,536

65,534

 

8

255.255.255.0

256

254

256

254

9

255.255.128.0

512

510

32,768

32,766

 

9

255.255.255.128

512

510

128

126

10

255.255.192.0

1,024

1,022

16,384

16,382

 

10

255.255.255.192

1,024

1,022

64

62

11

255.255.224.0

2,048

2,046

8,192

8,190

 

11

255.255.255.224

2,048

2,046

32

30

12

255.255.240.0

4,096

4,094

4,096

4,094

 

12

255.255.255.240

4,096

4,094

16

14

13

255.255.248.0

8,192

8,190

2,048

2,046

 

13

255.255.255.248

8,192

8,190

8

6

14

255.255.252.0

16,384

16,382

1,024

1,022

 

14

255.255.255.252

16,384

16,382

4

2

15

255.255.254.0

32,768

32,766

512

510

 

 

 

 

 

 

 

16

255.255.255.0

65,536

65,534

256

254

 

Class C License

N.N.N.H

 

 

 

17

255.255.255.128

131,072

131,070

128

126

 

# of Bits

 

Total #

Useable #

Total #

Useable

18

255.255.255.192

262,144

262,142

64

62

 

Borrowed

Subnet Mask

Subnets

Subnets

Hosts

# Hosts

19

255.255.255.224

524,288

524,286

32

30

 

2

255.255.255.192

4

2

64

62

20

255.255.255.240

1,048,576

1,048,574

16

14

 

3

255.255.255.224

8

6

32

30

21

255.255.255.248

2,097,152

2,097,150

8

6

 

4

255.255.255.240

16

14

16

14

22

255.255.255.252

4,194,304

4,194,302

4

2

 

5

255.255.255.248

32

30

8

6

 

 

 

 

 

 

 

6

255.255.255.252

64

62

4

2

NOTE: You must borrow at least 2 bits and you must leave at least 2 bits.

G. Wright Education Service Center Region XI, Ft. Worth, TX glwright@esc11.net