Start at .0 and add your magic number repeatedly.

The tells you where the line is drawn between these two parts.

The "IP Subnetting from Zero to Guru PDF" offers several benefits to readers:

In the early days, we used "Classes." This was wasteful and rigid. 255.0.0.0 (/8) — Massive corporations. Class B: 255.255.0.0 (/16) — Universities/Medium biz. Class C: 255.255.255.0 (/24) — Small offices/Homes.

At 11:55 AM, Leo didn't reach for a calculator. He closed his eyes. For a /27 mask, he knew the magic number was 32. He mapped out 192.168.10.0 , .32 , .64 , .96 ... all the way up [4, 6].