Variable Length Subnet Mask (VLSM)

Hi Rene,

I was trying to figure out a way of “knowing” the amount of bits needed for huge hosts without the need of a calculator, like:

  • 2^X-2= hosts (too complicated).

This way sorts the problem!

"
255.255.255.0 /24 – 256 addresses
255.255.255.128 /25 – 128 addresses
255.255.255.192 /26 – 64 addresses
255.255.255.224 /27 – 32 addresses

You can see that whenever the subnet becomes smaller, we can only use half of the addresses. I can apply the same logic if I move into the other direction:

255.255.240.0 /21 – 2048 addresses
255.255.248.0 /22 – 1024 addresses
255.255.254.0 /23 – 512 addresses
255.255.255.0 /24 – 256 addresses"

Thanks!