# IP Sub-Networking Mini-Howto

## Robert Hart, `hartr@interweft.com.au`

v1.0, 31 March 1997

This document describes why and how to subnetwork an IP network - that is using a single A, B or C Class network number to function correctly on several interconnected networks.

## 1. Copyright

## 2. Introduction

- 2.1 Other sources of information

## 3. The Anatomy of IP numbers

- 3.1 IP numbers belong to Interfaces - NOT hosts!
- 3.2 IP Numbers as "Dotted Quads"
- 3.3 Classes of IP Networks
- 3.4 Network numbers, interface addresses and broadcast addresses
- 3.5 The network mask

## 4. What are subnets?

## 5. Why subnetwork?

## 6. How to subnetwork a IP network number

- 6.1 Setting up the physical connectivity
- 6.2 Subnetwork sizing
- 6.3 Calculating the subnetwork mask and network numbers

## 7. Routing

- 7.1 The routing tables