Classes of IP Addresses

In our last article on “What is an IP address?”, we had discussed about what is an IP address, structure of an 32-bit IP address or to say an IPv4 address.. We had also mentioned about classes of IP addresses..

In this article we will be discussing on these classes of IP addresses..

But before that let’s recollect that an IP address is simply a unique number assigned to every device on a network.. and the octets of IP address are used to create classes of IP addresses. The Class of the address determines which part belongs to the network address and which part belongs to the node address.

Lets have a look at these IP classes now..

There are five IP classes plus certain special addresses :

Class A Network -- binary address start with 0, therefore the decimal number can be anywhere from 1 to 126. The first 8 bits (the first octet) identify the network and the remaining 24 bits indicate the host within the network. An example of a Class A IP address is 102.168.212.226, where "102" identifies the network and "168.212.226" identifies the host on that network. These addresses are for large networks with many devices.

Class B Network -- binary addresses start with 10, therefore the decimal number can be anywhere from 128 to 191. (The number 127 is reserved for loopback and is used for internal testing on the local machine.) The first 16 bits (the first two octets) identify the network and the remaining 16 bits indicate the host within the network. An example of a Class B IP address is 168.212.226.204 where "168.212" identifies the network and "226.204" identifies the host on that network. These addresses are for medium-sized networks.

Class C Network -- binary addresses start with 110, therefore the decimal number can be anywhere from 192 to 223. The first 24 bits (the first three octets) identify the network and the remaining 8 bits indicate the host within the network. An example of a Class C IP address is 200.168.212.226 where "200.168.212" identifies the network and "226" identifies the host on that network. These addresses are for small networks (fewer than 256 devices).

Class D Network -- binary addresses start with 1110, therefore the decimal number can be anywhere from 224 to 239. Class D networks are used to support multicasting. These addresses are multicast addresses.

Class E Network -- binary addresses start with 1111, therefore the decimal number can be anywhere from 240 to 255. Class E networks are used for experimentation. They have never been documented or utilized in a standard way.

Out of the almost 4.3 billion possible combinations, certain values are restricted from use as typical IP addresses. For example, the IP address 0.0.0.0 is reserved for the default network and the address 255.255.255.255 is used for broadcasts.

Since numbers are usually assigned to internet service providers within region-based blocks, an IP address can often be used to identify the region or country from which a computer is connecting to the Internet. An IP address can sometimes be used to show the user's general location.

The Internet Assigned Numbers Authority (IANA) manages the IP address space allocations globally. IANA works in cooperation with five Regional Internet Registries (RIRs) to allocate IP address blocks to Local Internet Registries (Internet service providers) and other entities.

Before ending this topic, lets also discuss on static and dynamic IPs.

At one time ISPs used to issue one IP address to each user. These are called static IP addresses. Because there are a limited number of IP addresses and with increased usage of the internet, ISPs now issue IP addresses in a dynamic fashion out of a pool of IP addresses. These are referred to as dynamic IP addresses. This also limits the ability of the user to host websites, mail servers, ftp servers, etc. In addition to users connecting to the internet, with virtual hosting, a single machine can act like multiple machines (with multiple domain names and IP addresses).

References:

• http://www.howstuffworks.com/
• http://en.Wikipedia.org/
• http://www.webopedia.com/
• http://www.searchwindevelopment.com/

What is an IP Address?

IP address is a very common term that we hear in our everyday life. Lets discuss in detail what exactly an IP address is..

Every device connected to the public Internet is assigned a unique number known as an Internet Protocol (IP) address. This number uniquely identifies the device and distinguishes it from other devices on the network. Networks using the TCP/IP protocol route messages based on the IP address of the destination.

Within an isolated network, you can assign IP addresses at random as long as each one is unique. However, connecting a private network to the Internet requires using registered IP addresses (called Internet addresses) to avoid duplicates.

Now lets see how an IP address looks like..

An IP address consists of four numbers separated by periods (also called a ‘dotted-quad’) and typically looks like 122.169.25.39. To make it easier for us (humans) to read and remember, IP addresses are normally expressed in decimal format as a "dotted decimal number" like the one above. But computers communicate in binary form.

Look at the same IP address in binary : 00111010.10101001.00011001.

The four numbers in an IP address are called octets, because they each have eight positions when viewed in binary form. If you add all the positions together, you get 32, which is why IP addresses are considered 32-bit numbers. Since each of the eight positions can have two different states (1 or 0) the total number of possible combinations per octet is 28 or 256. So each octet can contain any value between 0 and 255. Combine the four octets and you get 232 or a possible 4,294,967,296 unique values !

Now, this design of IP as a 32-bit number was developed by the original designers of TCP/IP and this system, now named as Internet Protocol version 4 or IPv4 is still in use. However, due to the enormous growth of the Internet and the resulting depletion of the address space, a new addressing system (IPv6), using 128 bits for the address, has also been developed. Both the systems of IP addressing are being used.

Continuing with the structure of IP address.. The octets, about which we were discussing, serve a purpose other than simply separating the numbers. They are used to create classes of IP addresses that can be assigned to a particular business, government or other entity based on size and need. The octets are split into two sections: Net and Host. The Net section always contains the first octet. It is used to identify the network that a computer belongs to. Host (sometimes referred to as Node) identifies the actual computer on the network. The Host section always contains the last octet.

The Class of the address determines which part belongs to the network address and which part belongs to the node address. All nodes on a given network share the same network prefix but must have a unique host number.

There are five IP classes plus certain special IP addresses..about which we will be discussing in our next article..

References:

• http://www.howstuffworks.com/
• http://en.Wikipedia.org/
• http://www.webopedia.com/
• http://www.searchwindevelopment.com/