What is IPv4?

IP address versions i.e. IPv4 and IPv6 transmit data in form of packets having a 4-bit IP version number as the first field of its header. There are only two versions of IP address (IPv4 and IPv6) are available in the internet market. However, the original IPv4 protocol is outdated but still in use on the internet. IP stands for Internet Protocol and it is the unique identity of any computer or mobile device over the Internet network. In this article “What is IPv4“, we will discuss the history, advantages, disadvantages, and various characteristics of IP version 4.


Internet Protocol (IP) versions

Based on data carried by packets that hold the IP addresses, Internet Protocol (IP) can be assigned in various version numbers between 0-15. This is because an IP version carried only a 4-bit field, hence it can’t be assigned above 15.

However, there are only two versions that are in use today in Internet markets are IPv4 and IPv6.

List of different IP versions

IP version


0 Reserved
1-3 Unassigned
4 Internet Protocol Version 4 -Active
5 Internet Stream Protocol (ST/ST-II)-Obsolete
6 Internet Protocol Version 6 (IPv6)
7 TP/IX- Obsolete
8 P Internet Protocol (PIP)- Obsolete
9 IPv9 (April fool day’s joke)
10-14 Unassigned
15 Reserved

However, there are only two versions that are in use today in Internet markets are IPv4 and IPv6.

What is IPv4

IPv4 stands for Internet Protocol Version Four. It was first introduced in early 1983 within ARPANET for production. These addresses are 32-bits binary numbers and expressed in Decimal/Hexadecimal formats instead of binary notation.

IPv4 addresses contain two sub-addresses (identifiers) separated by an imaginary boundary. These are as follows:

  • Network address
  • Host address

An IP address is a combination of 4 octets separated by dots and ranges from 0 to 255. This means each octet can range from minimum to maximum However, generally, IP addresses are expressed in binary form, but for better human understanding, IPv4 addresses are expressed in decimal/Hexadecimal formats.

Example: can be an IPv4 address that represents a 32-binary number.

These binary numbers determine the Network Class of each IP address.

Parts of IPv4

It contains the following parts:

  1. Network Part: Numbers that specify the address of Network
  2. Host Part: Numbers that specify the host to that network
IPv4 Parts: Network, Host and Subnet Mask
IPv4 Parts: Network, Host, and Subnet Mask

3. Subnet Mask: Number that species or differentiate between both Network and Host addresses means, which part of address belongs to Network and which parts belong to Host.

Characteristics of IPv4

Internet Version 4 or IPv4 contains the following characteristics.

  • It is a 32-bit size numeric address and each bit is separated by dots.
  • It is divided into 4 octets and each octet represents the number from 0 to 255.
  • The range of IPv4 is varied from 0 to 255.
  • It allows for a maximum of 4,294,967,296 (232) unique addresses.
  • It uses all styles of addresses such as Unicast, broadcast, and multicast.
  • It supports Virtual Length Subnet Mask (VLSM).
  • It contains 12 header fields and the length of the header is 20.
  • To map with Mac addresses, it uses Post Address Resolution Protocol.
  • It is expressed in dotted-decimal notation.
  • Network in IPv4 can be designed either manually or with DHCP.

Advantages of IPv4

IP version 4 addresses are 32-bits binary numbers and allow for a maximum of 4,294,967,296 (232) unique addresses and each bit is separated by dots. Hence, it is expressed in dotted-decimal format.

However, a typical IP address is expressed in binary form but we humans understand the decimal format easily, so IPv4 is expressed and written in decimal form.

It also uses security permits encryption which helps to maintain it more private and secure. Network allocation in IPv4 is easy than another addressing system.

It supports multi-devices simultaneously to communicate with good quality service or economical knowledge transfer. It permits flawless encoding and is redefined in nature. Further, it supports all styles of data communication i.e. Unicast, Broadcast, and Multicast.

Disadvantages of IPv4

  1. It consists of the limited space to assign addresses. The size of the address space is quickly depleted with the continuous increase in the devices connected over the internet network.
  2. It was deployed originally for the isolated military network but later it was adopted by public education and research network, hence It has security problems in data communication.
  3. It limits the header size which restricts to accommodate additional parameters to headers. This makes the protocol extensibility weak.
  4. As the Internet was first developed in the USA so almost 50% or more IP addresses are already reserved for the USA.

What is the subnet mask?

Subnet Mask number specifies or differentiates between both the Network and Host addresses that mean which part of address belongs to Network and which parts belong to Host.

An IP address contains both the Network and a unique Host interface on that network. The subnet mask tells about where the network address part ends and the Host address part begins in IP addresses. Subnet masks are also expressed in dotted decimal form.

If an IP address is expressed in the binary form then,

  • All bits set to 1 are part of the Network address.
  • And, bits set to 0 will be the part of Host address.

Note: The bits in the subnet mask will be consecutive ones and mostly start with 255 and continue on until the network mask ends.

Example: A class C subnet mask would be like

IP address: Classes in IPv4

IP address assignment on the network entirely depends on Internet Corporation for Assigned Names and Numbers. Based on the requirement of hosts per network, Internet Protocol version 4 or IPv4 is broken into five classes as follows:

  • Class A
  • Class B
  • Class C
  • Class D
  • Class E

Note: All these classes of IP addresses can be identified by the first octet of the address.

How to find the Network and Host number in an IP address?

You can use the below formula to find the total number of networks and Host per class in an IP address.

Network and Host number in IPv4
Network and Host number in IPv4
  • Number of Networks: 2Network bits
  • Number of Host per Network: 2Host bits-2

When calculating the number of hosts per network, two IPs are always subtracted from the total IPs because the first IP of a network is always reserved for the network number and the last IP is reserved for Broadcast IP. Refer above formula to find the number of Host per Network (2Host bits-2).

Also Recommended: Classes in IP address

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