What is Subnet Mask and What is Subnetting ? ( Part 2 )

Before starting this tutorials I will suggest you that please read the " What is subnet Mask and What is Subnetting ? ( Part 1 )

So lets start .....

Prefix Notation

A subnet mask is written in the decimal or 32 bit binary number form. Prefix is an alternative represent the mask. Table 1 lists the default subnet masks using the network prefix notation for the subnet mask.

Address Class                            Bits for Subnet Mask                      Network Prefix

Class A                 11111111 00000000 00000000 00000000                /8

Class B                 11111111 11111111 00000000 00000000                 /16

Class C                 11111111 11111111 11111111 00000000                  /24

For example, the class B network ID 138.96.0.0 with the subnet mask of 255.255.0.0 would be expressed in network prefix notation as 138.96.0.0/16.

Here 1 is known as Network bits or on bits

and  0 is known as Host bits or off bits.

The individual subnets and hosts can be determined through two basic formulas.

• Number of subnets = 2ⁿ where n is the number of bits borrowed to make the subnet mask or Number of borrowed on bits.
• Number of host per subnet =   2x-2
• Number of Bock size = 256 - New subnet 

So here I am taking an example 

sappose I take a 10.0.0.1 and prefix is /11

Solution    

10.0.0.1   subnet prefix - /11

Then, Default subnet mask = 255.0.0.0

In subnet prefix notation = 255.11100000.0.0

Then Number of subnets = 2^{n  _}23 =8

Number of Bock size = 256 -

Number of host per subnet =   2x-2 =  2power 5 -2 =30

Number of Bock size = 256 -224 (as given in table which is in part 1)

=32

So I make a table

Block size   0   32   64   96  128  160  192   224

First IP       1   33    65   97   129  161  193  225

                   .     .       .     .       .         .     .       .

                   .     .       .     .       .         .     .       .

                   .     .       .     .       .         .     .       .

Last IP        30  62   94   126  158   190 222  254

Block IP      31  63   95   127   159   191 223  255