What an IPv4 address is, how the network and host parts split, and which ranges are private.
IPv4 Addressing
In brief
Objectives
- Read an IPv4 address
- Explain the network/host split
- Recognise the private ranges
An IPv4 address is 32 bits, written as four numbers 0–255 separated by dots: 192.168.1.42. Part of it identifies the network, and the rest identifies the host on that network. A subnet mask draws the line between the two.
| Range | Use |
|---|---|
10.0.0.0/8 |
Private — large networks |
192.168.0.0/16 |
Private — home and small office |
127.0.0.0/8 |
Loopback — your own machine |
Note
Private ranges never appear on the public internet. Your 192.168.x.x address is reused in millions of homes — NAT (two sections on) is what lets it reach the outside.
Recap
- 32 bits, four numbers 0–255
- The mask splits network from host
- Private ranges never cross the public internet