TCP/IP Addressing

To set up a home network using TCP/IP will require you to allocate an IP address to each of the computers. How should you determine what values you should allocate to the computers on your home network which will also access the internet? Well, let's start with how individual IP addresses are defined and what they mean with regard to networking and the internet.

A TCP/IP network uses IP addresses to identify each of the computers (or in some cases parts of computers) attached to a network. An IP address consists of four hexadecimal numbers each between zero and 255 [hex FF]. When writing these down we normally write the decimal numbers separated by dots. The address for one computer on a network might be 192.168.0.1.

Networks can be defined in one of three different classes (called A, B, and C) which use a mask to define which part of the IP address is common across the network and which part changes to identify each computer.

A class C network uses a mask of 255.255.255.0 and can have 254 different addresses. The first three numbers in the address (matching the 255s in the mask) must all have the same value on a class C network. Also you can't use zero or 255 in the last number of the address as these have special meanings.

Class B networks use a mask of 255.255.0.0 and can have 65,024 (256x254) computers on the network and class A networks use a mask of 255.0.0.0 and can have 16,646,144 (256x256x254) computers on the same network. Obviously for home use, a class C network should be quite sufficient.

The internet is also a network even bigger than a class A network. To enable the internet to coexist with private networks, a number of address ranges have been set aside for private networks (classes A through C) and all other IP addresses are assumed to be internet IP addresses. The reserved number ranges are 10.0.0.0 through 10.255.255.255 which is one class A network, 172.16.0.0 through 172.31.255.255 which allows 16 separate class B networks, and 192.168.0.0 through 192.168.255.255 which allows 256 separate class C networks. If you set up your network using one of these address ranges then all IP addresses that are not within your selected network range will be referred to the internet by your proxy server (the computer that acts as a gateway between your system and the internet).

Given the above information on IP addresses your best option when allocating IP addresses to the computers on your home network is to assign 192.168.0.1 to the first computer followed by 192.168.0.2 for the second and so on.

 

This article written by Stephen Chapman, Felgall Pty Ltd.

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