SUBNETTING

Example 

A small organization is given a block with the beginning address and the prefix length 205.16.37.24/29 (in slash notation). What is the range, last address and no of addresses in the block?

Solution

The no. of addresses in the block = 2^32-n.

Here n=29 , Therefore 32-n=3.

The total no of addresses in the block is = 2³= 8

The last address of the block is = 205.16.37.31

Range of the block is from 205.16.37.24 to 205.16.37.31

SUBNETTING

ü   Clusters of networks are called subnets.

ü   An organization is normally assigned a large block of   address.

ü  Dividing a large block of address between the different    subnets is called subnetting .

ü   The organization has its own mask, each subnet must also have its own mask.

Example 

An organization is granted the block 130.34.12.64/26. The organization needs to have four subnets. What are the subnet addresses and the range of addresses for each subnet?

Solution

n=26. Therefore, 32-n=6

This means the total number of addresses in the block is 64 (2⁶).

If we create four subnets, each subnet will have 16 addresses.

Subnet

ü   No. of addresses= 16= 2^32-n     

ü   Therefore, n= 28 , i.e. the mask is 28 for each subnet

ü   The subnet mask is then /28.

Subnet 1: 130.34.12.64/28 to 130.34.12.79/28.

Subnet 2 : 130.34.12.80/28 to 130.34.12.95/28.

Subnet 3: 130.34.12.96/28 to 130.34.12.111/28.

Subnet 4: 130.34.12.112/28 to 130.34.12.127/28.