**IPV4 Introduction**

- The identifier used in the IP layer of the TCP/IP protocol suite to identify each device connected to the Internet is called the Internet address or IP address.
- An IPv4 address is a 32-bit address that uniquely and universally defines the connection of a host or a router to the Internet.
- IP address is the address of the interface.
- Pv4 addresses are unique. They are unique in the sense that each address defines one, and only one, connection to the Internet.
- Two devices on the Internet can never have the same address at the same time.
- However, if a device has two connections to the Internet, via two networks, it has two IPv4 addresses.
- The IPv4 addresses are universal in the sense that the addressing system must be accepted by any host that wants to be connected to the Internet.

**Notation**

There are three common notations to show an IPv4 address: binary notation (base 2), dotted-decimal notation (base 256), and hexadecimal notation (base 16).

*Binary Notation: Base 2*- In binary notation, an IPv4 address is displayed as 32 bits with spaces inserted between each octet/byte (8 bits) for easy reading.
- IPv4 address referred to as a 32-bit address, a 4-octet address, or a 4-byte address.

*Example: IPv4 address in binary notation:*

*01110101 10010101 00011101 11101010*

*Dotted-Decimal Notation: Base 256*- To make address more compact and easier to read, an IPv4 address is usually written in decimal form with a decimal point (dot) separating the bytes. This format is referred to as dotted-decimal notation.
- Each number in the dotted-decimal notation is between 0 and 255.

*Hexadecimal Notation: Base 16*__ometimes an IPv4 address in hexadecimal notation. Each hexadecimal digit is equivalent to four bits. This means that a 32-bit address has 8 hexadecimal digits. This notation is often used in network programming.__

*S*
A group of 4 bits with its hexadecimal equivalent. the hexadecimal notation has no added spaces or dots; however, 0X (or 0x) is added at the beginning or the subscript 16 at the end to show that the number is in hexadecimal.

*Example*

*a. 0X810B0BEF or 810B0BEF*

_{16}*b. 0XC1831BFF or C1831BFF*

_{16}**Address Space**

- A protocol like IPv4 that defines addresses has an address space. An address space is the total number of addresses used by the protocol.
- If a protocol uses b bits to define an address, the address space is 2 b because each bit can have two different values (0 or 1).
- IPv4 uses 32-bit addresses, which means that the address space is 2 32 or 4,294,967,296 (more than four billion).

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