IPv4 Addressing Explained

What an IPv4 Address Is

An IPv4 address uniquely identifies a device on a network, letting other devices know where to send data. It's written as four numbers separated by dots, each ranging from 0 to 255.

192.168.1.10
 |    |  |  |
 8    8  8  8   bits each = 32 bits total

Two Parts: Network and Host

Every IP address splits into a network portion (identifying which network a device belongs to) and a host portion (identifying the specific device within that network). Where exactly that split happens is determined by the subnet mask, covered in the next note in this section.

A Quick Look at Address Ranges

Private vs Public Addresses

Private addresses (like the 192.168.x.x range most home routers use) only have meaning inside a local network and are not directly reachable from the internet. Public addresses are globally unique and directly routable across the entire internet. NAT (covered in its own section) is the mechanism that lets many devices using private addresses share a single public address.

Why IPv4 Addresses Are Running Out

32 bits allows for roughly 4.3 billion unique addresses - a huge number in the 1980s, but far too few for a planet with billions of internet-connected devices today. This scarcity is the main reason IPv6 (covered later in this section) was developed.