| Home |
| Basic Networking |
| Hardware |
| Ethernet Networks |
| Wireless Networks |
| Configuration Tutorials |
| About This Site |
DIY Networks - Networking Basics
IP Addresses
Our focus on this website is TCP/IP networking. TCP/IP stands for Transmission Control Protocol/Internet Protocol and it is the method of transmitting data that is used throughout the world for the internet and most private networks. Indeed, the internet would not work without it. Fortunately, we shall concentrate on how to use TCP/IP rather than how it works.
What are IP addresses and what do they do? To the uninitiated they must appear to be a confusing jumble of numbers but IP addresses are much easier to understand than they first appear. Our intention when we create a network is to join computers and other devices together using cables or wireless technology (or a mixture of both) so that they can communicate with each other. They might be sharing files, a printer and an internet connection or perhaps just networked together for some LAN (Local Area Network) games but regardless of why you need a network there must be a way for each computer on the network to be uniquely identified and thats what IP addresses do.
A typical IP address is a group of four numbers between 0 and 255 seperated by full stops. Our example to the right has an IP address of 192.168.1.10 . The first 3 groups of numbers, the 192.168.1 part of the address identify this machine as belonging to the 192.168.1 network. The last number, 10 identifies this machine uniquely on the 192.168.1 network, which may have computers or devices numbered from 192.168.1.1 all the way to 192.168.1.254. You can think of it as like a street address, after all how would your visitors find you or your postman deliver your mail without a street address? So in human terms we can think of 192.168.1.10 as state.city.street.housenumber.
Looking at the example diagram to the right we have three computers connected to a local area network via ethernet cables and a switch. The first computer is 192.168.1.1, the second computer is 192.168.1.2 and the third computer is 192.168.1.3. Each computers IP address must have a unique last number or there will be two computers with the same IP address and things will work unexpectedly if they work at all. Because these three computers are on the same network they can be configured to share resources etc. If there was a fourth computer with an IP address of 192.168.2.4 it would not be able to see the other computers because it is on a different network, the first 3 groups of numbers are not the same. It could be on any IP address 192.168.2.1 - 192.168.2.254 and the other machines would be oblivious to it.
On the internet IP addresses are assigned to servers so that things like email and web sites work properly. For these servers to work properly they must have unique IP addresses, ones that are not used anywhere else in the entire world. Because of this there are special ranges of IP's that are designated for use in places like private LAN's (Local Area Networks) such as we intend to build. When you start configuring your network please use an address out of these address spaces-
- 10.0.0.0 – 10.255.255.255
- 172.16.0.0 – 172.31.255.255
- 192.168.0.0 – 192.168.255.255
- 169.254.0.0 – 169.254.255.255
Subnet Masks
The vast majority of the time when you are configuring a computer or a device to use a network you will be asked for a subnet mask. The subnet mask used in all of our examples throughout this website is 255.255.255.0, probably the most common netmask in the world. The netmask allows you to adjust the size of your network according to your needs. Changing the netmask to 255.255.0.0 would make our network larger and 192.168.1.1 would be able to see 192.168.2.4 as part of its network. Changing it to 255.255.255.248 would make it far smaller and 192.168.1.1 would not be able to see 192.168.1.10 as it would be on a different network. Subnetting is completely unnecessary for the small or medium sized home or office network so we will not cover it in other further detail than this, to avoid confusing the issue. Ensure that all of your computers and devices have the same netmask of 255.255.255.0 in their configuration and you will be fine.Gateway or Router Address
One of the most commonly used advantages of networking computers is the ability to share an internet connection and have all of your computers and devices able to access the internet at the same time, usually using an ADSL or cable connection or whatever form of broadband is commonly used in your area. Of course sharing an internet connection is not limited to broadband, you can share a dialup connection effectively accross your network as well. When your configuring a computer or device you may be prompted for a gateway or router address. This is the IP address of your adsl or cable modem as shown in our diagram to the right. In our diagram the ADSL modem has an IP address of 192.168.1.1 and the computers that use it to connect to the internet have IP addresses 192.168.1.2, 192.168.1.3 and 192.168.1.4. So the gateway address set on these machines is the address of the adsl modem, 192.168.1.1. Whenever a machine attempts to access resources not on the Local Area Network it will direct its request to the gateway, which will then retrieve the data and send it to the appropriate computer.