Lesson 03 — IP classes & private networks

IP classes were the original way the internet was organized — replaced in 1993 by CIDR. They still appear in documentation and on the plant floor, so it's worth knowing them. This lesson covers Class A / B / C, why 127 is reserved for loopback, the three private ranges (10.x, 172.16–31.x, 192.168.x), and which addresses you should never assign.