MY CCIE JOURNEY

this is the final one and interesting one


130.100.0.0

we need 30 subnets

each subnet with atleast 1000 hosts


class b ..

so subnet mask is 255.255.x.x

we need 30 right .. so tick in the subnet table until we meet the requirement

after looking at the table ..we ticked 5 of the subnet ones ..so even tick the 5 bits of upper subnets

it ends at 248 so our subnet mask is 255.255.248.0

now we have unticked three of them

(252 ,254 , 255 ***********important (3 of the unticked third octet and 8 of the remaining 4th octet so a total of 11..so tick 11 in the host bits portion and

subtract 2 to get the number of hosts)


the crucial one


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


128-------------*

192-------------*

224------------*

240-------------*

248--------------*

252

254

255


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

2--------------------*------------------------------*

4---------------------*------------------------------*

8----------------------*------------------------------*

16---------------------*-------------------------------*

32----------------------*(we met 30 here)-------------*

64------------------------------------------------------*

128-----------------------------------------------------*


256------------------------------------------------------*


512-------------------------------------------------------*


1024-----------------------------------------------------*

2048----------------------------------------------------* (total of 11 bits ticked 2048 - 2 = 2046 hosts / subnet)





hope this helped anyone ... any comments / suggestions are warmly welcomed ...


regards
rakesh