Understanding Technology One at a Time!!!

Share on Facebook

Share on Facebook

Share on Facebook

last class a

20.100.55.3 / 26

multiple of 8 again .. it ends at 24…to get to 26 we need to have two bits .. so tick two bits vertically and horizontally in the table two ..

under subnets it stopped at 192

so our subnet mask is

255.255.255.192

and under bits it stopped at 64 .. so the subnets increment at rate of 64

lets start with zero subnet

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

20.0.0.0

20.0.0.64

20.0.0.128

20.0.0.192

etc

etc till our ip

20.100.55.0———-20.100.55.1———-20.100.55.62———20.100.55.63

our ip falls here ..

20.100.55.64

20.100.55.128

20.100.55.192

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

Share on Facebook

moving on to class a

10.210.204.70/12

multiples of 8 …. 12 is not greater than 16 .. so multiple of 8 satisfying it is …8…so to get 12 we need to add 4 more bits …

there fore ..tick 4 bits horizontally and 4 bits vertically and game over

seeing the table under subnets it stops at 240..so remember we have only one multiple of 8 .. so only one 255 in subnet mask..

therefore subnet mask is 255.240.0.0

now seeing under bits section…it has stopped at 16 so…multiples of 16 or difference of 16 ..we need to start with zero —- for class a x.0.0.0

subnet————firsthost————–lasthost———–broadcast

10.0.0.0

10.16.0.0

10.32.0.0

etc till our ip

10.208.0.0——-10.208.0.1———10.223.255.254———–10.223.255.255

this satisfies our ip

10.224.0.0

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

Share on Facebook

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

Share on Facebook

Share on Facebook

another class c example

192.200.200.167 / 28

now again count till 24 …now are left with another 4 bits … rest is childs play as usual… tick 4 horizontally and 4 vertically in the second table…

after seeing the table and seeing the number under subnets it is 240 and under bits it is 16 .. so simple subnet mask ends with 240 and it has a diff of 16 for every

so our subnet mask is … 255.255.255.240

subnet we write

so we will start with 0 as usual

subnet————–firsthost————lasthost————–broadcast

192.200.200.0——-192.200.200.1——————–

192.200.200.16

192.200.200.32

192.200.200.48

etc

etc with increments of 16

192.200.200.160—–192.200.200.161—–192.200.200.174—192.200.200.175

our need fills here

192.200.200.176

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

Share on Facebook

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

Share on Facebook

i found these techniques in subnetting secrets and found them very effective hoping that these will help you too

firstly you need to have remember two tables …

1.basic table of first host , last host table

2.the crucial one to all calculation table …

here are the two

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

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

********************************************************************************
*********************************************

let me check with the formatter , if it comes correctly i will go ahead explaining the
concept if not i will host it to image shack and explain it

regards
RAKESH

Share on Facebook