In this tutorial, I’ll discuss about how to divide a network segment or ip with the vlsm method.  VLSM (Varialbe Length Subnet Mask) that are method to divide one ip network to some network segment with different needs and uses on different number of client for each network.

for the example on your network, you’re being configure network and they have some access for needs to computer lab as much as 50 clients, for wireless network as much as 120 clients and then for server needs as much as 10 clients and you given only 10.10.10.0/24  for network ip.

Based on the example, that mean we have 3 needs for different network with different client number’s.

The first step, we must to sort the needs based on biggest needs to the less as the following step :

• Wireless Network : 120 client/host
• Computer Lab.     : 50 client/host
• Servers.                 : 10 client/host

Then determine of prefix that could sufficient for each network needs as the following step.

• Wireless : 120 host (can be use /25 prefix that are have 126 valid host).
• Lab         : 50 host (can be use /26 prefix that are have 62 valid host).
• Servers  : 10 host (can be use /28 prefix that are have 14 valid host).

Next step we must define the subnetting table for divide the each network.

Wireless

For wireless network using /25 which one have subnetmask 255.255.255.128 and ip number 128 (256-128). then for counting of subnetting table are :

• Network    :  0
• First Host :  1
• Last Host  : 126
• Broadcast : 127

Computer Lab

and then for the next counting use host that haven’t used in preceding counting of subnet table.  for lab using /26 which one have subnetmask 255.255.255.192 and ip number are 64 (256-192). then calculate of subnetting table :

• Network : 128
• First Host : 129
• Last Host : 190
• Broadcast : 191

Servers

And the last for server network are use /28 prefix which one have subnetmask 255.255.255.240 and ip number 16 (256-240).

• Network : 192
• First Host : 193
• Last Host : 106
• Broadcast : 107

The result of network calculate with VLSM are : 

• Wireless :  have valid ip between 10.10.10.1 – 10.10.10.126 with subnetmask are 255.255.255.128
• Lab :  have valid ip between 10.10.10.129 – 10.10.10.190 with subnetmask are 255.255.255.192
• Servers : have valid ip between 10.10.10.193 – 10.10.10.106 with subnetmask are 255.255.255.240