Every internet device receives messages through an IP address. Understanding the rules and design behind that address — not just knowing the number — is a major asset for network troubleshooting and programming.
An IPv4 address is a 32-bit binary number divided into four 8-bit sections. For readability, each section is shown in decimal from 0.0.0.0 to 255.255.255.255 separated by dots. The address splits into a Network ID (the group the device belongs to) and a Host ID (the specific device within that group).
Early internet adoption used classes to divide addresses efficiently. - **Class A (0.x.x.x ~ 127.x.x.x):** For large organizations; only the first octet is the network ID. - **Class B (128.x.x.x ~ 191.x.x.x):** For medium-to-large organizations. - **Class C (192.x.x.x ~ 223.x.x.x):** For small networks; home router private ranges are typical examples. Today, the more flexible CIDR (Classless Inter-Domain Routing) method is used instead of strict classes.
A subnet mask filters which part of an IP is the network address and which is the host address. For example, 255.255.255.0 means the first three octets (24 bits) are the network, so devices in the same network can communicate directly without a router, and the last octet (8 bits) allows up to 254 hosts on one network.