Yesterday we looked into extending your knowledge of IP Addresses which led us through an IP Address’s octets, binary code connection and into IP classes which is where we’re going to pick up the subject today.

As we discussed there are five main IP classes that you should be aware of as well as a couple of special cases such as the Default Network and the Broadcast Network.

Default Network;

This class is the IP Address 0.0.0.0 which is specifically saved for the default network.

Class A;

This class is reserved for the larger networks – think BBC or MSN. These big players need the larger networks and can be identified by their IP Addresses by looking at the first Octet. If the first Octet is between 1 and 126 then it belongs to the Class A Network. The following three Octets will be used to recognise the host.

The Class A Network is huge and accounts for around half of the IP Addresses around the globe!

Loopback;

Specifically the IP Address 127.0.0.1 is the loopback address which is used by the host computer to send a message back to itself in order to discover any issues with the network for example.

Class B;

This class is used for medium sized networks such as universities or large colleges. As Class A Networks were made up of the first octet being between 1 and 126, Class B Networks are made up of the first octet being between 128 and 191.

In a Class B Network the first two sets of octets are used to identify the Net and the second two sets work to recognise the Host. Class B Networks are make up around a quarter of all the IP Addresses in the world.

Class C;

One step down, Class C Networks are used for smaller sized businesses and their IP Addresses comprise of a first octet ranging from 192 to 223. This class incorporates the first three sets of octets to recognise the Net and the last octet identifies the Host.

Class C IP Addresses make up around an eighth of the total IP Addresses used.
Classes D and E;

These classes are a little different to the other IP Classes – they each make up around a sixteenth of all IP Addresses. For Class D networks the first second and third bit values are 1 and the fourth is 0. The other 28 bits are used to identify the group of computers that the message is aimed at.

Class E Networks are made up of the first four values being 1 and again the following 28 bits act in the same way as Class E Networks. Class E, however, is used for experimental purposes.

Broadcast Network;

The final class is intended to carry all the messages from computers and the IP Address for this Network is 255.255.255.255.

Let us know if this has helped you to understand the complex world of IP Addresses a little better – now hopefully you can go away and stun your friends with all your newly gained knowledge!