Curso de Preparación para el Examen de CCNA 200-120 | Page 43

What is VLSM
Variable Length Subnet Masks allow you a much tighter control over
your addressing scheme. If you use a class C address with a default subnet
mask you end up with one subnet containing 256 addresses. By using VLSM
you can adjust the number of subnets and number of addresses depending
on the specific needs of your network. The same rules apply to a class A or
B addresses.
VLSM is supported by Cisco, OSPF, Dual IS-IS, BGP-4, and EIGRP.
You need to configure your router for Variable Length Subnet Masking by
setting up one of these protocols. Then configure the subnet masks of the
various interfaces in the IP address interface sub-command. To use
supernet you must also configure IP classless routes.

The Box Method
The box method is the simplest way to visualize the breakdown of a
range of addresses into smaller different sized subnets.
Start with a square. The whole square
is a single subnet comprised of 256
addresses.

/24
255.255.255.0
256 Hosts
1 Subnet

0

255
1