What/Why is IP Subnetting/VLSM? Not How

Answered Question
Feb 15th, 2008

Guy I want to know about IP Adreesing/VLSM.

Recently I have an interview. & ask about the same question. But I only answered the HOW part not WHAT & WHY.or you say any peoper defination.


I have also searched on net after that but not found WHAT & WHY part.


As I know How to do on paper all about that.

Correct Answer by Jon Marshall about 9 years 1 week ago

Hi


What is VLSM = the ability to apply different subnet masks to the same major network rather than having to use the same subnet mask.


WHY = because without VLSM you can have very inefficient address allocation eg.


192.168.5.0/24


You need a subnet that allows for 60 hosts and a subnet for a point to point link.


Without VLSM


60 host subnet = 192.168.5.0/26 or 255.255.255.192.


P2P link wher you only need 2 IP addresses =


192.168.5.64/26


And you have wasted 60 addresses.


With VLSM


192.168.5.0/26

192.168.5.64/30


Jon

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Correct Answer
Jon Marshall Fri, 02/15/2008 - 02:36

Hi


What is VLSM = the ability to apply different subnet masks to the same major network rather than having to use the same subnet mask.


WHY = because without VLSM you can have very inefficient address allocation eg.


192.168.5.0/24


You need a subnet that allows for 60 hosts and a subnet for a point to point link.


Without VLSM


60 host subnet = 192.168.5.0/26 or 255.255.255.192.


P2P link wher you only need 2 IP addresses =


192.168.5.64/26


And you have wasted 60 addresses.


With VLSM


192.168.5.0/26

192.168.5.64/30


Jon

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