Private vs Public IP Addresses

IP addresses are unique identifiers that allow devices to communicate over the Internet. There are two main types of IP addresses: private and public. In this blog post, we will explain the difference between them and how they are used in different scenarios.

What is a private IP address?

A private IP address is an IP address that is only valid within a specific network, such as a home or a corporate network. Private IP addresses are not visible to the outside world and cannot be used to access the Internet directly. They are usually assigned by a router or a DHCP server within the network.

Private IP addresses are useful for internal communication between devices on the same network, such as sharing files, printers, or other resources. They also help to conserve the limited number of public IP addresses available.

There are three ranges of private IP addresses defined by the Internet Assigned Numbers Authority (IANA):

10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.168.0.0 to 192.168.255.255

These ranges are reserved for private use and cannot be assigned to any public device or network.

What is a public IP address?

A public IP address is an IP address that is globally unique and can be accessed by anyone on the Internet. Public IP addresses are assigned by Internet Service Providers (ISPs) or other organizations that manage public networks.

Public IP addresses are necessary for devices that need to communicate with the Internet, such as web servers, email servers, or online gaming consoles. They also allow devices on different networks to communicate with each other.

Public IP addresses can be either static or dynamic. A static IP address is fixed and does not change over time, while a dynamic IP address is assigned temporarily and can change periodically.

How do private and public IP addresses work together?

Private and public IP addresses work together through a process called Network Address Translation (NAT). NAT is a technique that allows devices with private IP addresses to access the Internet using a public IP address.

NAT works by mapping one or more private IP addresses to a single public IP address, usually provided by a router or a gateway device. The router or gateway device keeps track of which private device is using which port number on the public IP address, and forwards the incoming and outgoing packets accordingly.

NAT has several benefits, such as:

It allows multiple devices to share a single public IP address, saving costs and resources.
It enhances security by hiding the internal structure and details of the private network from the outside world.
It enables devices with different types of IP addresses (such as IPv4 and IPv6) to communicate with each other.

What are IPv4 and IPv6 formats?

IPv4 and IPv6 are two versions of the Internet Protocol that define how IP addresses are formatted and structured.

IPv4 is the older and more widely used version of the Internet Protocol. It uses 32-bit addresses, which can accommodate up to 4.3 billion unique devices on the Internet. However, due to the rapid growth of the Internet, IPv4 addresses are running out and cannot meet the demand for new devices and services.

IPv6 is the newer and more advanced version of the Internet Protocol. It uses 128-bit addresses, which can accommodate up to 340 undecillion (3.4 x 10^38) unique devices on the Internet. IPv6 also offers other features and benefits, such as improved security, performance, and scalability.

The format of IPv4 and IPv6 addresses is different:

An IPv4 address consists of four decimal numbers separated by dots, such as 192.168.1.1.
An IPv6 address consists of eight hexadecimal numbers separated by colons, such as 2001:db8::1.

Examples of private and public IP addresses in both formats

Here are some examples of private and public IP addresses in both IPv4 and IPv6 formats:

| Type | Format | Example | |---------|--------|------------------| | Private | IPv4 | 10.0.0.1 | | Private | IPv6 | fd00::1 | | Public | IPv4 | 203.0.113.1 | | Public | IPv6 | 2001:db8:abcd::1 |

Note that fd00::/8 is a range of private IPv6 addresses defined by RFC 4193, similar to the private IPv4 ranges defined by RFC 1918.