wonder[riya7wonder[riya7 Banned Posts: 41 ■■□□□□□□□□
In class he did variable length subnet masks. What is it and how does one do sums with it?


  • NissekiNisseki Member Posts: 160
    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[riya7wonder[riya7 Banned Posts: 41 ■■□□□□□□□□
    I got the book. How long will it take to read the book?
  • Welly_59Welly_59 Member Posts: 431
    Less time if you actually started rather than asking
  • CryptoQueCryptoQue Member Posts: 204 ■■■□□□□□□□
    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 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 =
    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 =
    Finance =
    Public Relations =

    New IP Ranges
    HR = -
    Finance = -
    Public Relations = -

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