====== IPv4 ======

**IPv4 (Internet Protocol version 4)** is the fourth version of the Internet Protocol and the most widely deployed protocol for identifying devices on IP networks.

An IPv4 address is a **32-bit** number that uniquely identifies a network interface.

Example:

<code>
203.0.113.25
</code>

Although IPv6 has been introduced, IPv4 remains the dominant protocol on today's Internet.

-----

===== IPv4 Address Format =====

An IPv4 address consists of **32 bits** divided into four groups of eight bits (called **octets**).

Example:

<code>
203.0.113.25

↓

11001011.00000000.01110001.00011001
</code>

Each octet can have a value between:

<code>
0 – 255
</code>

Therefore an IPv4 address is written as:

<code>
x.x.x.x
</code>

where each **x** is between 0 and 255.

-----

===== Why 32 Bits? =====

A 32-bit address provides:

<code>
2^32

=

4,294,967,296
</code>

possible addresses.

Although this seems like a large number, it is no longer sufficient for today's Internet.

This shortage led to the development of IPv6.

-----

===== Public and Private IPv4 Addresses =====

IPv4 addresses are divided into:

  * Public addresses
  * Private addresses

Public addresses are globally routable on the Internet.

Private addresses are used within local networks and are translated to public addresses through Network Address Translation (NAT).

See also:

  * [[networking:internet:private-public|Private vs Public IP]]
  * [[networking:internet:nat|Network Address Translation (NAT)]]

-----

===== Network and Host =====

An IPv4 address consists of two logical parts:

  * Network portion
  * Host portion

Example:

<code>
192.168.1.25/24

Network:
192.168.1

Host:
25
</code>

The boundary between the network and host portions is determined by the subnet mask or CIDR prefix.

-----

===== Special IPv4 Addresses =====

Some IPv4 addresses have special purposes.

^ Address Range ^ Purpose ^
| 127.0.0.0/8 | Loopback |
| 169.254.0.0/16 | Link-local (APIPA) |
| 10.0.0.0/8 | Private network |
| 172.16.0.0/12 | Private network |
| 192.168.0.0/16 | Private network |
| 255.255.255.255 | Limited broadcast |

These addresses are reserved and cannot always be used as ordinary public addresses.

-----

===== IPv4 Address Exhaustion =====

The number of available IPv4 addresses is limited.

As Internet usage grew, the supply of public IPv4 addresses became exhausted.

Several technologies help reduce IPv4 consumption:

  * NAT
  * Private addressing
  * CIDR
  * Dynamic address allocation (DHCP)

Ultimately, IPv6 was developed to overcome this limitation.

-----

===== IPv4 vs IPv6 =====

^ IPv4 ^ IPv6 ^
| 32 bits | 128 bits |
| About 4.3 billion addresses | Vast address space |
| Decimal notation | Hexadecimal notation |
| Widely deployed | Increasing adoption |
| NAT commonly used | NAT usually unnecessary |

-----

===== Checking an IPv4 Address =====

An IPv4 address can provide useful information such as:

  * Whether it is public or private.
  * Geographic location (approximate).
  * ASN (Autonomous System Number).
  * Reverse DNS (PTR).
  * Network owner.

-----

===== IPv4 and Telenegar =====

Several Telenegar tools work with IPv4 addresses.

  * [[tools:ipcheck|IP Check]]
  * [[tools:pingcheck|Ping Check]]
  * [[tools:traceroute|Traceroute]]
  * [[tools:portcheck|Port Check]]

These tools can help identify ownership, routing, connectivity, and DNS information associated with an IPv4 address.

-----

===== Common Misconceptions =====

  * **Every IPv4 address is publicly accessible.**
    * False. Many IPv4 addresses are private and cannot be reached directly from the Internet.

  * **IPv4 is obsolete.**
    * False. Although IPv6 is growing, IPv4 remains the most widely used Internet Protocol.

  * **An IPv4 address identifies a person.**
    * False. It identifies a network interface, not an individual.

-----

===== Related Topics =====

  * [[networking:internet:ip-addresses|IP Addresses]]
  * [[networking:internet:ipv6|IPv6]]
  * [[networking:internet:private-public|Private vs Public IP]]
  * [[networking:internet:subnetting|Subnetting]]
  * [[networking:internet:cidr-notation|CIDR Notation]]
  * [[networking:internet:nat|Network Address Translation (NAT)]]
  * [[tools:ipcheck|IP Check]]

-----

{{tag>ipv4 ip internet networking cidr subnet nat}}