CCNA TRAINING -AN INTRODUCTION TO THE IP ADDRESS CLASSES

       

IP ADDRESS:
Every computer that access internet has a unique identifying number which is known as the IP address of that computer. IP address is always expressed as in four decimal number format for example 192.168.1.1, this is how we humans understand and remember the IP address but computers understand the same IP in binary form. IP addresses are 32 bit addresses.
IP addressing is simply configuring each host with a unique and a valid IP address. An IP basically has two parts; the network part (numbers to the left) and the host part (numbers to the right). The network part of the IP address identifies a particular network on the internet it is the netID, whereas on the other hand the host part of the IP address identifies the host or the workstations that are connected on that network, it is the hosted.
IP addresses are organized in form of classes or address formats according to the number of the bytes (first byte represents the network); this is because networks vary in sizes. First few bits of an IP address determine the class it’s using. There are four different classes:
• Class A:
These addresses are for large networks with large number of total hosts.
• Class B:
These addresses are for medium-sized networks.
• Class C:
These addresses are for small (LAN) networks.
• Class D:
These addresses are multicast addresses and are not allocated to the hosts.

IP addresses are placed in a particular class on the basis of the decimal values of their first octet.
• Class A address first octet has decimal values from 1 to 127, (127 is reserved)
• Class B address first octet has decimal values from 128 to 191
• Class C address first octet has decimal values from 192 to 223
• Class D address first octet has decimal values from 224 to 239, with four left most bits as 1110.
Number of hosts on each class:
• Class A: 16,777,214 hosts
• Class B: 65,532 hosts
• Class C: 254 hosts
• Class D: addresses are multicast addresses

Number of networks on each class:
• Class A: 126 networks
• Class B: 16384 networks
• Class C: 2097152 networks
• Class D: addresses are multicast addresses
Format for class address:
Class A:
0 xxxxxxx XXXXXXXX XXXXXXXX XXXXXXXX
Class B:
10 xxxxxx xxxxxxxx XXXXXXXX XXXXXXXX
Class C:
110 xxxxx xxxxxxxx xxxxxxxx XXXXXXXX

Here:
x represents network
X represents computers

One important point to note is that every network no matter what size and class it is from has a broadcast and network address that can’t be used at any point. This also means that when calculating IP addresses one must subtract 2 from the IP addresses within that network.

Article Directory : http://www.articlecube.com