← IP Addressing & Subnetting learning pathIP Addressing & Subnetting · Module 3 of 10
Address classes and private ranges
Know IPv4 classes and private address ranges.
📖 Key ideas
- Historic classes: A (1–126), B (128–191), C (192–223).
- Class D (224–239) is multicast; E is experimental.
- Private ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16.
- 127.0.0.0/8 is loopback (127.0.0.1 = localhost).
- Private addresses use NAT to reach the internet.
💡 Real-life example: Private IPs are internal phone extensions; NAT is the receptionist connecting them to outside lines.
Private IPAddress not routed on the internet
Loopback127.0.0.1, the device itself
NATNetwork Address Translation
MulticastOne-to-many delivery