IP Addressing Fundamentals
Internet Protocol (IP) addressing is a fundamental concept in networking that allows devices to communicate over the internet and local networks. This guide covers the basics of IP addressing and its importance in network communication.
What is an IP Address?
An IP address is a unique numerical identifier assigned to each device on a network. It serves two main purposes:
- Host or network interface identification
- Location addressing
IPv4 Structure
IPv4 addresses are 32-bit numbers usually expressed in dotted-decimal notation, divided into four octets (8 bits each). For example:
192.168.1.1
Each octet can range from 0 to 255, giving us a total of approximately 4.3 billion possible addresses (2^32).
Address Classes
Traditional IPv4 addressing defines five address classes:
| Class | First Octet Range | Default Subnet Mask | Use Case |
|---|---|---|---|
| A | 1-126 | 255.0.0.0 | Large organizations |
| B | 128-191 | 255.255.0.0 | Medium organizations |
| C | 192-223 | 255.255.255.0 | Small networks |
| D | 224-239 | N/A | Multicast |
| E | 240-255 | N/A | Reserved for research |
CIDR Notation
Classless Inter-Domain Routing (CIDR) replaced the traditional class system. It uses a suffix notation that specifies the number of network bits:
192.168.1.0/24
The /24 indicates that the first 24 bits are used for the network portion, leaving 8 bits for host addresses.
Special IP Addresses
Some IP addresses are reserved for special purposes:
- 0.0.0.0: Used to represent the default network
- 127.0.0.1: Localhost/loopback address
- 169.254.0.0/16: Link-local addresses
- 192.168.0.0/16: Private network addresses
- 10.0.0.0/8: Private network addresses
- 172.16.0.0/12: Private network addresses
Next Steps
- Learn about Subnetting to understand how to divide networks into smaller segments
- Explore our CIDR Calculator to practice working with IP addresses and subnet masks
- Read about Routing to understand how IP addresses are used in network routing