VLSM

VLSM Example

VLSM stands for Variable Length Subnet Mask is the ability to specify a different subnet mask for the same network number on different subnets. Put on other words; its a method that allow multiple levels of subnetworked IP addresses within a single network.

Understanding the VLSM capabilities and how to implement it  is important when planning large networks, VLSM is a crucial component of an effective IP-addressing plan for a scalable network and eventually it leads to better understanding of route summarization and CIDR.

“Online VLSM Calculater” on my blog and “VLSM Subnet Calculator” are two of the best online Subnet Calculators out there, They are intend for automate and simplify VLSM calculation process, However you can find subnet calc’s software which you can download as well, Hopefully I can talk about these softwares in the near future if I could spare some times for it.

In addition to saving your time the website is easy to use, convenient and a hundred percent accurate.. its highly recommended for beginners and advanced users.

Some benefits of VLSM:

  • It enables to vary the size of each subnet, based on the needs of that subnet.
  • It offers more efficient use of IP addresses so it saves lots of IPs,which are wasted instead.
  • It allows more than one subnet mask to exist withing a network allows subnetting of an already subnetted network address. This hierarchical levels  gives a great capability to use route summarization.
  • It Isolates the topology changes from other routers.

Note that not all routing protocols support VLSM such as RIPv1 or IGRP.
The routing protocols: RIPv2, OSPF, Dual IS-IS, BGP-4, and EIGRP do support the advertisement of subnet information.

Download Subnet calc software (HTML based)

Image source: http://www.hill2dot0.com


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