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ciscowanabe · Nov 8, 2006, 12:41 PM

Hi all Im new here and need some help with my project as im stumped. I currently going through for "networking admin." and now in to Cisco. 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

Tuoder · Nov 8, 2006, 02:58 PM

Google "subnet calculators". There are a bunch of Java-based ones that should simplify your endeavor quite a bit. I think that you could probably find one for dowload, if you look. I use Boson Subnet calculator on PCs.

ciscowanabe · Nov 8, 2006, 04:21 PM

thank you tuoder, much appreciated, i will do that.