What Is TCP/IP(IPv4)

IPv4 what it is.

Let’s start with IP first If we want to start the an ethical hacking then we have to know about IP it is also known as TCP/IP.TCP/IP is today’s most popular network protocol and is the protocol in the Internet. It is a routable protocol that provides connection between multifarious systems, without IP we can’t imagine internet connectivity; for example it allows communication between same or different operating systems like Linux, Unix, Windows, Novell Netware and Mac OS computers spread over multiple interconnected networks . The “TCP/IP protocol” is actually the “TCP/IP suite” composed of many different protocols each with its own functions. The two main protocols are in its name: the Internet Protocol and the Transmission Control Protocol. It is divided into two parts :-

· IPv4 (Internet Protocol Version 4)

· IPv6 (Internet Protocol Version 6)


Today I am goanna briefly introduce about IPv4 . It’s a very vast topic but if you want to know deep facts about IPv4 then you can search on Google. IPv4 addressing is assigning a 32-bit logical numeric address to a network device. Every IP address on the network must be unique. An IP address is represented in a dotted decimal format, for example: 134.51.24.8. As you can see the address is divided in 4 parts, these parts are called octets. The current used addressing schema in IPV4 is divided in 5 Classes:

Address Class	IP address range	Default Subnet Mask	Number of Networks	Number of Hosts	CIDR	Known as
Class A	1-126	255.0.0.0	126	16,777,214	/8	Private IP
Class B	128-191	255.255.0.0	16,384	65,534	/16	Public IP
Class C	192-223	255.255.255.0	2,097,152	254	/24	Real Public IP
Class D	224-239	Multicast	n/a	n/a	n/a
Class E	240-255	Reserved	n/a	n/a	n/a

In a class A network, the first octet defines the network portion of the address. The last three octets are used for host addresses and subnet masking.

Network.Host.Host.Host
255.0.0.0

In a class B network, the first two octets define the network portion of the address. The last two octets are used for host addresses and subnet masking.

Network.Network.Host.Host
255.255.0.0

In a class C network, the first three octets define the network portion of the address. The last octet is used for host addresses and subnet masking.

Network.Network.Network.Host
255.255.255.0

A private network is commonly known as an Intranet.

The Internet Assigned Numbers Authority (IANA) has set aside the following IP address range for Intranet networks.

Private IP Address

IANA reserved 4 address ranges to be used in private networks; these addresses won’t appear on the Internet avoiding IP address conflicts

10.0.0.0 through 10.255.255.255
172.16.0.0 through 172.31.255.255
192.168.0.0 through 192.168.255.255

Special Address

Loopback Address 127.0.0.1 (use for loopback testing)

Automatic Private IP Addressing

(APIPA) is a feature of Windows-based operating systems that enables a computer to automatically assign itself an IP address when there is no Dynamic Host Configuration Protocol (DHCP) server available to perform that function. APIPA serves as a DHCP server failover mechanism and makes it easier to configure and support small local area networks (LANs).

169.254.0.0 – 169.254.255.255

	192	224	240	248	252	254	255
128	64	32	16	8	4	2	1
I	I	I	I	I	I	I	I

Now take the remainder and convert that to decimal. Here we have 4 left, so :
8+4+2+1= 15. You can use 15 IP addresses only, instead of the 255 normally allocated.