CLASS B TRICKY EXAMPLE  

Wednesday, October 29, 2008

this is some what tricky .. please do clear the concepts in the above cases

191.20.56.65 / 25 ------------

as usual ...greater than 24 .. so we need to add one more bit to make it 25 .. so tick in the table two one start horizontally and vertically and rest is gone

so seeing it ... we got under subnets the value is 128 .. so the subnet mask is

255.255.255.128

now going on with next ..we got 128 under bits so the difference is 128..but now we need to have four octet subnets for every third octet one .. if this

confuses you see the below table

start with 0------------since class b -------------x.x.0.0

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

191.20.0.0

191.20.0.128

191.20.1.0

191.20.1.128

191.20.2.0

191.20.2.128

etc etc till our ip

191.20.56.0----------191.20.56.1-------191.20.56.126---------191.20.56.127

this satisfies our ip

191.20.56.128


hence in this way this can be determined




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

64

128


256


512


1024

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