Subnetting explained

World’s simplest 2 step IPv4 subnetting - for all classes.

Before we get to know what these steps are we need to understand the following:

·         Each and every IPv4 address consists of 4 octets in the form of W. X .Y . Z, each containing 8 bits and that means a total of 32 bits .

·         These four octets are divided into 2 portions called NETWORK PORTION (N.P) and HOST PORTION (H.P).

·         Based on the no. of octets divided for both N.P and H.P we have

CLASS –A:  W. X .Y . Z   i.e.  1 network octet and 3 host octets

CLASS –B :  W . X .Y . Z   i.e.  2 network octets and 2 host octets

CLASS –C :  W . X .Y . Z   i.e.  3 network octet and 1 host octet

(Here the underlined part represents the network portion and the rest is host portion)

·         W,X,Y and Z are decimal equivalents of  any  octet (set of 8 bits)  and the octet’s value ranges from  00000000 to  11111111 i.e  from 0 to 255 (total of 256 values)in decimals.

(We are not discussing ipv4 in detail and hence only the necessary points are being considered )

·         The default subnet mask for each class are :

CLASS –A: 255. 0 . 0 . 0    /8          =11111111.00000000.00000000.00000000

CLASS –B: 255 .255 . 0. 0 /16       =11111111.11111111.00000000.00000000

CLASS –C: 255 .255 .255 .0 /24    =11111111.11111111.11111111.00000000

Let us move to subnetting 

(continued in next post)