Lesson 1

Determining IP Addressing Requirements

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Lesson 1: Determining IP Addressing Requirements

TCP/IP is the most popular protocol suite for data network installations, but not

because it is the easiest to set up. When, during network infrastructure planning, you

decide to use TCP/IP, you must be aware of the additional effort this decision implies.

Network administrators must configure every TCP/IP computer with a unique IP

address, as well as with other configuration parameters. Before administrators can do

this, however, they must determine what types of IP addresses to use, based on the

communication requirements of the network.

After this lesson, you will be able to

■ Understand the difference between public and private IP addresses

■ List the IP address ranges designated by the Internet Assigned Numbers Authority

(IANA) for private use

■ Describe how computers with private IP addresses are able to access the Internet

■ Understand the differences between a network address translation (NAT) router and a

proxy server

■ Specify which computers on a network should use public addresses and which should

use private addresses

Estimated lesson time: 20 minutes

Using Public and Private Addresses

The TCP/IP protocols use IP addresses to identify the computers on a network. Every

packet that a TCP/IP computer transmits contains the IP address of the computer that

is the packet’s intended recipient, and routers use that address to forward the packet to

the appropriate destination. For this system to function properly, every computer must

have a unique IP address. If duplicate addresses were to exist on the network, routers

would contain incorrect information and packets would end up in the wrong place.

On a private network, network administrators are responsible for ensuring that the

address assigned to every computer is unique. As long as the address assigned to

each computer is different, it doesn’t matter what addresses the administrators use, as

long as they subnet them properly. On a public network such as the Internet, how-

ever, IP address assignments are more complicated because the Internet consists of

thousands of connected networks, each with its own administrators. If the adminis-

trators of each network were to select their own IP addresses at random, duplication

and chaos would result.