Can someone explain this subnet problem

Question: Which subnet does host 10.225.14.98 255.255.240.0 belong to?

Answer: 10.225.0.0

Why is it that you have to go into the 3rd octect even though the increment is 16 which I got from 28-32= 16

32 being in the 4th octect.

Thx!

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Comments

dynamik

The third octet is the "interesting" octet.

255.255.240.0 = 11111111.11111111.11110000.00000000

That's where the division occurs.

shanparames

Can u tell 28-32=16

With regards

S.Swaminathan

dynamik

Where did you get 28 from? 255.255.255.240 is /28. 255.255.240.0 is /20, so you'll have 12 bits to use for host range (32-20).

nash0924

Don't know if this will allow you to figure out your problem.

0 0 0 0 1 0 1 0 = 10
1 1 1 0 0 0 0 1 = 225
0 0 0 0 1 1 1 0 = 14
0 1 1 0 0 0 1 0 = 98

10.255.14.98
00001010.11100001.00001110.01100010

255.255.240
11111111.11111111.11110000.00000000
anding(network addy) =
10.225.0.0
00001010.11100001.00000000.00000000

Kaminsky

Here's a tip that helped me here.

Very First Thing - It's a class A so subnet will be the ones from bit 9 onwards.

Use a dot when you write down the subnet so you don't lose your place and get confused.

In this instance 255.255.240.0:
the 2nd octet becomes " 0. ".
The 1's of the subnet mask run out in the 3rd octect so you do 256-240 = "16"

This makes your overall increment is "0.16" - If you just say 16 you may get yourself muddled whilst your learning it.

> B]10.255.0.0[/B
...
...... 10.255.14.98
...
> B]10.255.16.0[/B

and viola, you see your subnet. Using the dot saved me loads of grief and my sanity !

sambuca69

SurferdudeHB wrote: »

Question: Which subnet does host 10.225.14.98 255.255.240.0 belong to?

Answer: 10.225.0.0

Why is it that you have to go into the 3rd octect even though the increment is 16 which I got from 28-32= 16

32 being in the 4th octect.

Thx!

Convert 240 and you get 11110000. Take the lowest 1 bit and you've got 16 (128 64 32 16 8 4 2 1)

So every subnet will increment by 16.

captobvious

Subnetting Made Easy

This helped me tons when I first starting to understand subnetting.