Subnetting is basically breaking down a group of IP addresses in to smaller groups a way of managing IP addresses. With IPv4 we have a limited amount of IP adds that we can use so we have to manage them by subnetting

Let us consider this ip address

192.168.10.0

We all know ip address is made up of 4 octects...

we have seen similar ip addresses like

192.168.10.1 192.168.10.2.... 192.168.10.250 like that

Why there is no 192.168.10.256 or 192.168.10.300 or 300.1.5.258 ?

We all know ip addresses are represented in bit wise pattern

Ip address :- 32 bits (4 octets)

00000000.00000000.00000000.00000000
0. 0. 0. 0

11111111.1111111.11111111.1111111
255.255.255.255

So 0 is the minimum value
and 255 is the maximum value

Then in the case of a valid host..
For every network there should have to be a network id and broadcast id...
The first available ip address will be the network id and the last one will be the broadcast id

In this case...

192.168.10.0 :- The first available ip address

192.168.10.255 :- The last available ip address

First one will be the network id and the last one the broadcast id..

This rule is valid for every networks

Consider a case...

In your company you are in a situation like this...You have only one address pool or range ...Your boss asked you to create two networks from that pool...

So the real subnetting test begins...

Consider 192.168.10.0 is that range.....

In normal case

If we give an ip from the network 192.168.10.0
the default subnetmask will be 255.255.255.0


192.168.10.0
255.255.255.0 /24

No. of hosts = ?
For class c networks consider only the last octet of the subnetmask...

Last octet 0
Binary of 0 = 00000000
Then from that find the no. of networks and hosts

2 raised to no. of ones in that octet will be the no. of networks
2 raised to no. of zeros -2 will be the no. of hosts (explaination follows)

00000000
no.of ones :- 0 0*1= 1
no. of zeros :- 8 2*8-2 = 256-2 = 254


So the network range


192.168.10.0
192.168.10.1

192.168.10.253
192.168.10.254
10.192.168.10.255

So as per our rules

192.168.10.0 --- Network id

192.168.10.1 ----First available host

192.168.10.254 ----Last available host

192.168.10.255 ----- Last host

• Written by pradeep.
• In category Hardware & Troubleshooting.
• 14 years ago.

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