Hi Lawrence.
I really appreciate your kind explanation.
Please check if I understood correctly.
When subnet mask 12 changes to 13, I guess, according to what I have known
of, it is calculated like this: # of subnets with the mask 12 was 2^4 -2=14,
and # of subnets with the mask 13 will be 2^5-2=30 subnets.
Therefore, the increased # of subnet: 30-14=16 by increasing one more bit of
mask.
I think that with the subnet mask 12, I can have up to 14 subnets (2^4)-2
<---(This part is still not clear, because it seems to say that as long as I
have the subnet mask 12, whether it is class A, B, or C, it will always have
14 subnets. Is it correct?) How about this: 172.37.2.56/20<---This one also
looks to me that 4 extra bits have been borrowed from 3rd octet so that it
can have (2^4)-2=14 more subnets.)And how about this: 12.37.2.56/12<---This
one is class A. It looks to me that it also will have up to 14 subnets
simply it has /12. Am I missing something?
Wasn't the original ip address 172.37.2.56/12 one that belonged to
170.32.0.0/12 subnet whose range is 170.32.0.0 to 170.47.255.255?
Am I getting close to your point or am I uncontrollably misunderstanding?
Again, I appreciate your help.
I look forward to your reply.
Thanks very much.
Jeongwoo.
------Original Message------
From: [EMAIL PROTECTED] (Lawrence Dwyer)
To: jeongwoo park <[EMAIL PROTECTED]>, Groupstudy <[EMAIL PROTECTED]>
Sent: July 13, 2000 12:55:23 AM GMT
Subject: Re: 2 questions
As long as you only have the /12, and only your assigned address range
172.32.0.0-172.47.255.255 then there will be no more subnets.
Now you could move the bit masking to the right 1 bit and that would give
you 2
subnets with a /13..
/14 will give you 4 subnets, /15 will give you 8 subnets and so on. Each
move
of the masking bit by one, changes the # by a power of 2. Think of the word.
Sub Net. You are taking one large range of addresses and breaking it into
smaller ranges by increasing the bits in the subnet mask. Remember, a subnet
mask really only defines a range of addresses with a common network number
expressed in binary. Variable Length Subnet Masking (VLSM) just means that
you
can move that masking back and forth. As you increase the bits in the
subnet
mask, you are decreasing the range of possible addresses accepted by that
mask.
They are Sub Networks of your original range.
So
if you were to move your masking bit 1 to the right from /12 to /13
Then you are going from 11111111.11110000.0.0 (255.240.0.0)
to 11111111.11111000.0.0 (255.248.0.0) and you would have 2 sub networks of
your original network range.
172.32.0.0-172.39.255.255/13 and
172.40.0.0-172.47.255.255/13
If you remember the binary from the 1st answer 37 was 0010 0101
With 12 bits of masking, you have 4 bits in the 2nd octet, "locking in" the
0010
With 13 bits and now 2 subnets you are "locking in" 00100 and 00101 in two
seperate sub ranges
bits 12 13th address range
0010 0 000-111 is 32-39
0010 1 000-111 is 40-47
OK one more for clarification
With a /14 you are now increasing you mask by 2 bits from the original,
which
gives you 4 subnetworks.
bits 12 13th 14th add range
0010 0 0 00-11 is 32-35
0010 0 1 00-11 is 36-39
0010 1 0 00-11 is 40-43
0010 1 1 00-11 is 44-47
There was a range of 8 numbers in the second octet per network at /13, but
at
/14 that range was cut in half to 4 while the # of networks doubled. At /15
it
would do so again; range of 2 (32-33, 34-35,....,46-47) with 8 networks.
The network number is the 1st and the broadcast is the last in a particular
range.
The number of subnets is only limited by the mask you give it (up to a /30).
I really hope it helps, subnet theory can be quite an "Ah Ha!" experience,
once
you understand them, you can go backwards and forwards very easily.
:)
Larry
jeongwoo park wrote:
> Hi Lawrence!
> I have an additional question.
> How many subnets will this address 172.37.2.56/12 have?
> And what are they? What is the broadcast ip address in a particular
subnet?
> Could you tell me how you calculate?
> I am a tcp/ip newbie.
> I have read book about tcp/ip. But it confuse all the time.
> I will appreciate your help.
> Thanks in adv.
>
> ........................................................
> iWon.com http://www.iwon.com why wouldn't you?
> ........................................................
........................................................
iWon.com http://www.iwon.com why wouldn't you?
........................................................
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