MY CCIE JOURNEY

this is the first example


class c

identify subnet , first and last host of the following ip or what ever it may be

here is the example 1

192.168.12.68 / 25 ***************** 25 bits so ...

firstly count in multiples of 8 till we get 24 .... as one octet has 8 bits right ...

so 8 + 8 + 8 + (1) --------- left ..


rest is the childs play... really .. now go to the table 2 and borrow or tick 1 bit horizontally and vertically so in this case

see the table two and come back you will find number 128 under subnets and 128 under bits ..

so subnet is 128 and bits 128 indicate that difference should be 128 --->we will see this point later

so our subnet is


255.255.255.128



as we all know we need to start any subnet with 0 .. so start it


subnet---------firsthost---------------------lasthost-------broadcast

192.168.12.0------192.168.12.1-----192.168.12.126-----192.168.12.127

(see the difference of 128
which we got in bits )

192.168.12.128-------------------------------


hence in this way it can be determined


the crucial one


bits------128-------64-- ---32--------16--------8------4----2------1

subnets *** *(1 bit vertically)


128 **** *(1 bit horizontally)

192

224

240

248

252

254

255


powers of 2 --------------------------------------- subnets--------------------------------------hosts (-2)

2

4

8

16

32

64

128


256


512


1024


hence in this way it can be determined

more examples to follow .. let me know if this makes sense to anyone

regards
Rakesh