student networking admin (need help with a project) VLSM

[Lmm]

Hi all Im new here to the forum and need some help with my project as im stumped. I am currently going through for "networking admin." and now in to Cisco doing a project. I had to develop an IP addressing scheme for a larger network, which consists of 56 subnets with the first subnet containing 1-32 subnets and up to 800 hosts on each, and the second subnet 33-56 with up to 12 hosts on each. I had to choose a single class A private address to accommodate all the 56 subnets (which that was easy)
I chose 10.0.0.0 /14
which gave me:
10.0.0.0/14 10.0.0.1 - 10.3.255.254 and a broadcast address of 10.3.255.255
10.4.0.0/14 10.4.0.1 - 10.10.7.255.254 and a broadcast address of 10.7.255.255
all the way up and my last address being
10.252.0.0/14 10.252.0.1 - 10.255.255.254 and broadcast address of 10.255.255.255

now here is where my problem starts
I have to use VLSM to optimize the addressing scheme by further subdividing the last subnet. I have to choose a subnet mask that will generate enough subnets to accommodate all the 24 smaller subnets I created with enough host address space to accommodte all there 12 hosts.

so i choose 255.248.0.0 to give me 30 subnets with 524,286 hosts (of course adding the 2 to eachfor network and broadcast)
so using my last subnet which was 10.252.0.0/14

and my new mask of 255.248.0.0
my results dont seem to look right to me here is what i got. Does it look right and if not can someone help to let me know where Im going wrong please and thank you, greatly appreciated

Subnet Number Range of valid host addresses Broadcast address
10.248.0.0 /18 10.248.0.1 to 10.248.63.254 10.248.63.255
10.248.64.0 /18 10.248.64.1 to 10.248.127.254 10.248.127.255
10.248.128.0 /18 10.248.128.1 to 10.248.191.254 10.248.191.255
10.248.192.0 /18 10.248.192.1 to 10.248.255.254 10.248.255.255
10.249.0.0 /18 10.249.0.1 to 10.249.63.254 10.249.63.255
10.249.64.0 /18 10.249.64.1 to 10.249.127.254 10.249.127.255
10.249.128.0 /18 10.249.128.1 to 10.249.191.254 10.249.191.255
10.249.192.0 /18 10.249.192.1 to 10.249.255.254 10.249.255.255
10.250.0.0 /18 10.250.0.1 to 10.250.63.254 10.250.63.255
10.250.64.0 /18 10.250.64.1 to 10.250.127.254 10.250.127.255
10.250.128.0 /18 10.250.128.1 to 10.250.191.254 10.250.191.255
10.250.192.0 /18 10.250.192.1 to 10.250.255.254 10.250.255.255
10.251.0.0 /18 10.251.0.1 to 10.251.63.254 10.251.63.255

[fibox]

Hi...

/18 is 255.255.192.0 subnet

/14 is 255.248.0.0 subnet but it should give you 64 subnet with 262144 - 2 host

I am very confused with your posting..
Please correct me if I am wrong.. thanks guys.

[biggles77]

Lmm, could you EDIT your post to make the numbers easier to read. Maybe spread them out a little and change the colours and/or bold them like below. (This is just a suggestion, NOT a demand)

It breaks up the range, mask and broadcast so it makes it a bit easier to follow. Well fo my old eyes anyway.

10.248.0.0/18 - 10.248.0.1 to 10.248.63.254 - 10.248.63.255

[ssckrp]

Hi

THing is that you have subnetted already with 14bit mask.

From the derived subnets, you are selecting sub network 248 to further subnetting it for VLSM


which is not possible.

regards

prabu

[daviddavis]

Hi Lmm,
Thanks for your post!
Did you get your question answered?
Its good to have you in the forum!
-David

[ahmer_sahab]

Hi,

I am not too sure but I read some where that we can not use VLSM with Subnetting. Am I right guys?

[daviddavis]

Sure, you can use both subnetting and VLSM.

Subnetting is just taking a network and breaking it into smaller networks.

VLSM (variable length subnet mask) just means that the subnet mask doesn't have to be fixed (like 255.0.0.0, 255.255.0.0 or 255.255.255.0). The subnet mask can be 255.255.252.0 or 255.128.0.0 or 255.255.255.224.

Both of these work together. In networking today, you need to use both of these and they work great together.

Thanks for your post!

-David

[theterranaut]

Ahmer, further to David's post, here's a great- and free- resource for you:

http://www.3com.com/other/pdfs/infra..._US/501302.pdf

I've recommended this to loads of people, I've often wondered why its free!

regards,

theterranaut

[daviddavis]

Hi TT,

Good Doc, Thanks!

I will give you some reputation points for that & all your other posts!

-David

[fibox]

I will put my suggestion here.

I will use

/22 for the first 32 subnets with 800 hosts

10.0.0.0 - 10.0.3.255
:
:
10.0.128.0 - 10.0.131.255

and

/27 for the next 24 subnets with 12 hosts

10.0.132.0 - 10.0.132.31
:
10.0.132.224 - 10.0.132.255.255


10.1.132.0 - 10.1.132.31
:
10.1.132.224 - 10.1.132.255.255


10.2.132.0 - 10.2.132.31
:
10.2.132.224 - 10.2.132.255.255

Please correct me if I am wrong.

I do not know if Mr/Ms LMM will come back to take a look. But its good to have something we can practise on..