Overview
This lecture explains how IP addresses are structured, the different address classes (A, B, C, D), how to identify them, and their significance in networking.
IP Address Structure
- IP addresses are divided into a network ID and a host ID.
- In 9.100.100.100, "9" is the network ID (Class A), "100.100.100" is the host ID.
Address Class System
- The class system splits global IP space into multiple classes: A, B, C, D (and unspecified).
- Class A: first octet is network ID, last three octets are host ID.
- Class B: first two octets are network ID, last two are host ID.
- Class C: first three octets are network ID, last octet is host ID.
- Each class supports a different number of hosts per network.
Address Ranges & Bit Patterns
- Class A: first bit is 0; first octet range is 0–127; 16,777,216 addresses per network.
- Class B: first bits are 10; first octet range is 128–191.
- Class C: first bits are 110; first octet range is 192–223; 256 addresses per network.
- Class D: first bits are 1110; first octet range is 224–239; used for multicasting.
- Addresses outside these ranges are for unassigned/testing purposes.
Modern Context
- The class system has mostly been replaced by CIDR (Classless Inter-Domain Routing).
- Understanding address classes remains important for networking basics.
Key Terms & Definitions
- Octet — An 8-bit segment of an IP address (range: 0–255).
- Network ID — Portion of IP address identifying the network.
- Host ID — Portion of IP address identifying a specific device on the network.
- CIDR — Modern system for assigning IP addresses without class restrictions.
- Multicasting — Sending data to multiple recipients simultaneously (Class D use).
Action Items / Next Steps
- Review the differences between IP address classes and their address ranges.
- Read about CIDR for next class.