IP4 Address Scheme

The IP4 addressing scheme uses a series of 4 bytes. This is called dotted decimal notation when viewed in Base 10. Example: Networking equipment, of course, sees them in Binary, which looks to them like this:

Each number is one byte in size (256 possible numbers from 0 to 255). This gives us 2 32 possible address ID numbers for the whole Internet. Each number is called an Octet.

We don’t see or type the address numbers. We type in words or phrases like and a DNS (Domain Name Server) in the system translates our words into the appropriate numbers.

The IP4 addressing scheme is broken down into groups of networks based on size, and distributed using the binary numbering system to segment the entire network into these groups. Since it is binary, every time we cut a slice, we have to do it exactly in half, or by 2.

Let’s use a circle to represent the entire Internet.

The first group of addresses are Class A. These start with the addresses and go thru Think of the addresses as working like an automobile speedometer. It starts with The next number is then etc. till you get to Then it rolls over to and starts all over again. It all ends with Networks are determined by the first octet.

The first group of addresses are Class A. These start with the addresses and go thru

Class A networks 0 – 127 have the first octet assigned, but are free to use the other numbers for their equipment, often called hosts.

can be considered: Network. Host. Host. Host This gives Class A networks 2 24 hosts in each network. 2 to the power of 24 =

network includes all numbers from thru

There are few Class A networks (128), but each one is huge in size.

Cutting the remainder of the available numbers in half gives us our Class B networks. These run from to

Like the Class A’s, the Class B networks are also divided into an assigned network number, and the remaining host segments, however the assigned number not only takes the first octet, but the second one as well can be considered: Network. Network. Host. Host This gives Class B networks 2 16 hosts in each network. 2 to the power of 16 =

includes all numbers from to is a completely different Class B network. Consider the network. The next Class B network would be the network, followed by the network……etc….. There are a lot more Class B’s than Class A’s.

There are more Class B networks (65,536), but each one is smaller than a Class A in size. 65,536 hosts in each Class B network.

Class C networks do the process all over again. Cut the remaining portion in half, and 12.5% of the numbers are left.

Class C networks run from to Class C’s, like Class B’s, take more octets for their network portion of their address. This leaves very little left for the hosts.

can be considered: Network. Network. Network. Host This gives Class C networks 2 8 or 256 hosts in each network. However, there are 2 to the power of 24 = networks ! ! !

includes all numbers from to Network. Network. Network. Host is a completely different Class C network, as is , or even There are a lot more Class C’s than Class B’s, but each one is very small.

The remaining 12.5% is officially Class D & E, but these addresses are not issued to users, and are not discussed here. They are used for multicasting and experimentation.

If you look closely at binary numbers, you will see a lot of patterns and numbers that repeat. Hard drives, RAM, and other PC components use binary numbers to determine size. Notice the pattern of the zeros in the first octet in each network class.

Since IP4 has limited space for new network hosts, and the Internet is growing daily, Scientist and Engineers have developed a new networking strategy called IP6. IP6 uses Base 16 or Hexadecimal instead of base 2 for addressing. When IP6 is fully implemented, every square inch of the world’s surface can have its own IP address.