IP Addressing & IP Classes


An ip address is a numeric identifier assigned to each machine on an IP network. It designates the specific location of a device on the network. An ip ddress is a logical address not a physical address. Ip addressing was designed to allow hosts on one network to communicate with a host on a different network regardsless of the type of LANs the hosts are participating in.

IP Termonology

Bit : A bit is one digit either a 1 or a 0.
Byte : A byte is equal to 8 bits.
Octet : An octate ia made up of 8 bits, is just an ordinary 8-bit binary number format.
Network Address : This isthe designation used in routing to send packets to a remote network. Example 192.168.1.0, 10.0.0.0, 172.16.0.0.
Broadcast Address : The address is used by applications and hosts to send information to all nodes on a network is called the broadcast address. For example Layer 3 broadcast include 255.255.255.255

Subnet Mask

A Subnet mask is a 32-bit number that masks an IP address, and divides the IP address into network address and host address. Subnet Mask is made by setting network bits to all "1"s and setting host bits to all "0"s. Within a given network, two host addresses are reserved for special purpose, and cannot be assigned to hosts. The "0" address is assigned a network address and "255" is assigned to a broadcast address, and they cannot be assigned to hosts.

Examples of commonly used netmasks for classed networks are 8-bits (Class A), 16-bits (Class B) and 24-bits (Class C).

Hierarchical IP Addressing Scheme

An IP address consist of 32 bits of information. These bits are divided innto four sections, referred to as octates or bytes, with each containing 1 byte(8 bits). You can depict an IP address using one of the methods:
* Dotted-decimal, as in 172.16.30.56
* Binary, as in in 10101100.00010000.00011110.00111000

The 32-bit IP address is a structured or hierarchial address, as opposed to a flat address. Although either type of addressing scheme could have been used. The advantage of this scheme is that it can handle a large number of address namely 4.3 bilion. The disadvantage of the flat addressing scheme and the reason it's not used format Ip addressing, relates to routing. If every address were unique, all router on the internet woukd need to store the address of each and every machine on the internet. this would make efficient routing impossible, even if only a fraction of the possible addresses were used.
The solution to this problem is to use a two or three level hierarchial addressing scheme that is structured by network and host or by network, subnet and host.

IP Address & Classes

Internet Protocol (IP) is of 32 bit i.e 4 bye in decimal form. IP address has 5 classes i.e Class A, Class B, Class C, Class D and Class E.
Class A : 0-127 (127 is reserved for loopback)
Class B : 128-191
Class C : 192-223
Class D : 224-239 (Reserved for Multicasting)
Class E : 240-255 (Reserved for R&D and DOD)

IP addresses is also divided into Public(Used over Internet) and Private IP( Can used by Private Company) addresses.
Class A 10.0.0.0 to 10.255.255.255, Class B172.16.0.0 to 172.31.255.255 and in Class C 192.168.0.0 to 192.168.255.255 is Private address and rest are Public Address.

IP Class Format

Class A : Network.Host.Host.Host
Class B : Network.Network.Host.Host
Class C : Network.Network.Network.Host

IP Address Types

Loopback : Used to test the IP stack on the local computer. Can be any addresses from 127.0.0.0 to 127.255.255.255. Can be create by command
#int Loopback1
# ip add 127.0.0.2 255.0.0.0
L2 Broadcast : These are sent to all nodes on LAN
L3 Broadcast : These are sent to all nodes on Network
Unicast : This is an address for a single interface and these are used to send packet to a single destination host.
Multicast : These are packets sent from single source and transmitted to many devices on different network and can called one-to-many.