Vlsm

wonder[riya7

In class he did variable length subnet masks. What is it and how does one do sums with it?

Nisseki

What resources are you using to study for your cisco?

I'm using Todd Lammle's book and video series on IT Pro TV, he explains it quite well.

wonder[riya7

I got the book. How long will it take to read the book?

Welly_59

Less time if you actually started rather than asking

CryptoQue

wonder[riya7 VLSM is used to scale standard subnets (i.e. Class C) to fit network requirements. For example, if you're redesigning a network for a company that has 3 departments they want to keep isolated. Department 1 (HR) has 105 computers, department 2 (Finance) has 40 computers, and department 3 (Public Relations) has 55 computers. The company currently has all departments configured on a 192.168.1.0/24 network. You can use VLSM to meet the company's needs. You would breakdown the class C into smaller subnets that are comparable to the amount of hosts that will be connected.

Network Subnet = 192.168.1.0/24
HR = 105 computers = /25 = 126 usable IPs
Finance = 40 computers = /26 = 62 usable IPs <---couldn't use a /27 because the maximum usable IPs for it is only 30
Public Relations = 55 computers = 62 usable IPs

New Networks
HR = 192.168.1.0/25
Finance = 192.168.1.128/26
Public Relations = 192.168.1.192/26

New IP Ranges
HR = 192.168.1.1 - 192.168.1.126
Finance = 192.168.1.129 - 192.168.1.190
Public Relations = 192.168.1.193 - 192.168.1.254

*routing will need to be involved in this process, but that's a more detailed topic you can find a lot of research on.