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Monday, July 27, 2009

IP Subnetting

Subnetting

Subnetting used in IP network for many years the purpose of subnetting Is to break IP networks into multiple chunks , IP Network subnetting can be done for a variety of reasons, including organization, use of different physical media (such as Ethernet, FDDI, WAN, etc.), preservation of address space, and security. The most common reason is to control network traffic...

Subnet Masking

Applying a subnet mask to an IP address allows you to identify the network and node parts of the address. The network bits are represented by the 1s in the mask, and the node bits are represented by the 0s. Performing a bitwise logical AND operation between the IP address and the subnet mask results in the Network Address or Number.

For example, using our test IP address and the default Class B subnet mask, we get:

10001100.10110011.11110000.11001000      140.179.240.200   Class B IP Address
11111111.11111111.00000000.00000000      255.255.000.000   Default Class B Subnet Mask
--------------------------------------------------------
10001100.10110011.00000000.00000000      140.179.000.000   Network Address

Default subnet masks:

· Class A - 255.0.0.0 - 11111111.00000000.00000000.00000000

· Class B - 255.255.0.0 - 11111111.11111111.00000000.00000000

· Class C - 255.255.255.0 - 11111111.11111111.11111111.00000000

Allowed Class A Subnet and Host IP addresses

# bits

Subnet Mask

CIDR

# Subnets

# Hosts

Nets * Hosts

2

255.192.0.0

/10

2

4194302

8388604

3

255.224.0.0

/11

6

2097150

12582900

4

255.240.0.0

/12

14

1048574

14680036

5

255.248.0.0

/13

30

524286

15728580

6

255.252.0.0

/14

62

262142

16252804

7

255.254.0.0

/15

126

131070

16514820

8

255.255.0.0

/16

254

65534

16645636

9

255.255.128.0

/17

510

32766

16710660

10

255.255.192.0

/18

1022

16382

16742404

11

255.255.224.0

/19

2046

8190

16756740

12

255.255.240.0

/20

4094

4094

16760836

13

255.255.248.0

/21

8190

2046

16756740

14

255.255.252.0

/22

16382

1022

16742404

15

255.255.254.0

/23

32766

510

16710660

16

255.255.255.0

/24

65534

254

16645636

17

255.255.255.128

/25

131070

126

16514820

18

255.255.255.192

/26

262142

62

16252804

19

255.255.255.224

/27

524286

30

15728580

20

255.255.255.240

/28

1048574

14

14680036

21

255.255.255.248

/29

2097150

6

12582900

22

255.255.255.252

/30

4194302

2

8388604

Allowed Class B Subnet and Host IP addresses

# bits

Subnet Mask

CIDR

# Subnets

# Hosts

Nets * Hosts

2

255.255.192.0

/18

2

16382

32764

3

255.255.224.0

/19

6

8190

49140

4

255.255.240.0

/20

14

4094

57316

5

255.255.248.0

/21

30

2046

61380

6

255.255.252.0

/22

62

1022

63364

7

255.255.254.0

/23

126

510

64260

8

255.255.255.0

/24

254

254

64516

9

255.255.255.128

/25

510

126

64260

10

255.255.255.192

/26

1022

62

63364

11

255.255.255.224

/27

2046

30

61380

12

255.255.255.240

/28

4094

14

57316

13

255.255.255.248

/29

8190

6

49140

14

255.255.255.252

/30

16382

2

32764

Allowed Class C Subnet and Host IP addresses

# bits

Subnet Mask

CIDR

# Subnets

# Hosts

Nets * Hosts

2

255.255.255.192

/26

2

62

124

3

255.255.255.224

/27

6

30

180

4

255.255.255.240

/28

14

14

196

5

255.255.255.248

/29

30

6

180

6

255.255.255.252

/30

62

2

124

Logical Operations

This page will provide a brief review and explanation of the common logical bitwise operations AND, OR, XOR (Exclusive OR) and NOT. Logical operations are performed between two data bits (except for NOT). Bits can be either "1" or "0", and these operations are essential to performing digital math operations.
In the "truth tables" below, the input bits are in bold, and the results are plain.

AND

The logical AND operation compares 2 bits and if they are both "1", then the result is "1", otherwise, the result is "0".


0

1

0

0

0

1

0

1

OR

The logical OR operation compares 2 bits and if either or both bits are "1", then the result is "1", otherwise, the result is "0".


0

1

0

0

1

1

1

1

XOR

The logical XOR (Exclusive OR) operation compares 2 bits and if exactly one of them is "1" (i.e., if they are different values), then the result is "1"; otherwise (if the bits are the same), the result is "0".


0

1

0

0

1

1

1

0

NOT

The logical NOT operation simply changes the value of a single bit. If it is a "1", the result is "0"; if it is a "0", the result is "1". Note that this operation is different in that instead of comparing two bits, it is acting on a single bit.

0

1

1

0

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