Introduction

In order to understand and configure Cisco IOS Quality of Service mechanisms, it is imperative that you have a full understanding of IP addressing, variable-length subnet masks, and all types of access lists. Most of the Quality of Service mechanisms that you will learn to deploy throughout this book will be matched against access lists, so it is highly recommended that even experienced network administrators pay close attention to the material in this chapter.

IP addressing seems like a very simple thing to do, but if you are considering Quality of Service on your network, you will want to pay close attention to your addressing scheme. This is especially important in making access lists to filter traffic or classify traffic based on source and destination IP addresses. You will find it easier to define traffic in granular detail if your IP addresses have been properly assigned.

Network Address Translation (NAT) is also reviewed in this chapter. Although it is a valuable tool, NAT can create difficulties when you are matching access lists in order to classify or queue traffic. There are many things to consider before deploying NAT, but armed with the proper information, you will be able to make the best design decisions.

IP Address Classes and Classful IP Routing

Much like a street address within a city, the TCP/IP address defines the location of a participating node within the network. Each node in a TCP/IP network must possess an address to be able to participate within the...