IP Address Numbering Overview Part 2

So how does all this effect me?

It should become clear shortly, because of the numbering scheme outlined above, and because of the way blocks of address's were assigned in the early days of the internet, there is a shortage of unique IP address's.

This means that when you buy your $10/month hosting package (which is really a great deal when you consider what you get for it these days) you do not usually get your own unique IP address for your web site, you share it with others.

IP address are classified into 3 class's (groups) depending on the decimal equivalent of the 1st octet in the address as below:

0-255.xxx.xxx.xxx = all address's

Class A

Intended for a small number of networks that had a large number of computers (hosts) attached. Class A IP Address have a value in the range 1...126 as the first octet. The values 0 and 127 are not available because they have special uses. Class A addresses use the first octet to identify the network which means that 126 addresses are usable, each of which can support 16,777,216 computers (hosts).

Class B

Intended for some networks that had an intermediate number of computers (hosts) attached. Class B IP Addresses have a value in the range 128...191 as the first octet. Class B addresses use the first two octets to identify the network which means that 16,320 addresses are usable, each of which can support 65,536 computers (hosts).

Class C

Intended for a large number of networks that would have a small (relatively) number of computers (hosts) attached. Class C IP Addresses have a value in the range 192...223 as the first octet. Class C addresses use the first three octets to identify the network which means that 2,080,800 addresses are possible, each of which can support 254 computers (hosts).

In summary what this means is that it is more than likely that your web site will be sharing it's IP address with other web sites, there are a few possible serious problems that could arise that you should be aware of:

1. If you use either free or very cheap low cost hosting companies you could be sharing with some nasty or undesirable web sites. If these web sites end getting banned or black legged by the search engines for taking part in "illegal" search engine optimization techniques they may blacklist or down grade the IP address which will effect you as well, even though your site is fine.

2. If you use the same hosting company for many sites and then start linking these together to try and improve the page rank you may get into trouble. It is not that difficult for the search engines to work out the IP address of the sites linking to you. If it finds that they are all on the same IP address this may be considered as link spamming. After all what are the chances that a group of genuine links from a number of different web sites are all going to be hosted on the same computer - not likely!.

So the bottom line is that if you own several sites and want to link these sites together, for whatever reasons, it is safer to spread out the hosting amongst several hosting companies on different IP address's. This will reduce the possibility of your sites getting either banned or down graded by the search engines.