Did you know that my Terry’s Computer Tips email newsletter is published internationally and my Terry’s Computer Tips web site is viewed by visitors from at least 48 countries? This really is an International Internet.
During a recent week, I had visitors from the United States, the United Kingdom, Canada, Australia, Netherlands, India, Norway, Belgium, Spain, Turkey, Sweden, France, Germany, Republic of Korea, Philippines, New Zealand, Singapore, Malaysia, Finland, Mexico, Italy, Poland, South Africa, Switzerland, Ireland, Saudi Arabia, Denmark, via Satellite ISP, Israel, Bangladesh, Japan, Czech Republic, Islamic Republic of Iran, Puerto Rico, Belarus, Malta, Estonia, Costa Rica, Austria, United Arab Emirates, Qatar, Barbados, Pakistan, Brazil, Hong Kong, Indonesia, Lebanon, Guyana and a few where the IP address was not geographically-specific. The list is in order of the number of visitors.
You noticed the key term near the end of the list, didn’t you? The IP address is the key.
In order for your computer to talk to my web server, or to any other computer on the Internet, it has to provide an "Internet Protocol address" — an IP address.
Although you might think of my web server as www.TerrysComputerTips.com, the Domain Name System (DNS) exists to make Internet navigation easier for you and me, as humans.
Computers don’t need names to work on the Internet. They use IP addresses. The current IP address system is known as IPv4; that is, it is an Internet Protocol address and has 4 sets of numbers, each ranging from 0 to 255. For example, the IP address of www.google.com is 126.96.36.199.
A few of these values have special meanings, so you don’t often see 0 or 255, which are used for some blanket purposes.
Similarly, there are three reserved ranges of IP addresses that are designed for use by private networks. If you have a home network, you should be familiar with the most common range 192.168.x.y, because home wired routers usually default to using 192.168.0.1-192.168.0.254. Home wireless routers usually default to the 192.168.1.x range.
Where I’m using "x"” and "y" for two numbers ranging from 0 to 255, the flip side of the IP address is what the computers use for the same purpose — to define which numbers are valid within a given network.
The IP address for a network idenfities 4 numbers, separated by dots, such as 192.168.1.37 .
Each of these is an 8-bit number — that is, in binary (which is 0’s and 1’s), these are made up of 8 binary values. Each can be a 1 or a 0. So, the eight components are:
2 to the 7th power (= 128 or 0),
2 to the 6th power (= 64 or 0),
2 to the 5th power (= 32 or 0),
2 to the 4th power (= 16 or 0),
2 to the 3th power (= 8 or 0),
2 to the 2nd power (= 4 or 0),
2 to the 1st power (= 2 or 0),
2 to the 0th power (= 1 or 0).
So, 0100000 in binary is 64. Similarly 00000010 = 2, 255 is 11111111 in binary, and 0 is 00000000.
That’s why you see many things in the computer world referring to multiples of 2 — because, at its lowest level, each memory location really only stores two possible values, a 1 or a 0. It’s also why, if you get into any aspect of programming, most programs start counting with zero instead of starting with one.
Back to networks, the flip side of the IP address (which helps to define a specific network interface — e.g., a network card in a computer) is called the "netmask." The netmask used with an IP address to define a specific network. Just like the IP address, this is four 8-bit numbers, each ranging from 0 to 255.
But, in a netmask, each bit has a special meaning. If the bit is set (that is, if it has a value of 1), then it is significant in defining a network. If it is 0, then any IP address value for the corresponding bit is a wildcard and is part of the specific network.
Let’s look again at the home network using 192.168.1.x. Another way, the more common way, of writing this is to use an IP address and a netmask, written this way 192.168.1.1/255.255.255.0.
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