Every device connected to a network that implements the Internet protocol has a unique identification address assigned to it. This identification address is known as the IP Address. The collection of this interconnected network is referred to as the internet.

Sometimes, you see an IP Address for a device from outside the network. The device's IP Address may look different from what was assigned in the subnetwork. This is due to a mechanism called NAT. This different-looking IP Address from outside the network is an External IP Address.

The external IP Address, also known as the Public IP Address, is the address assigned to the router interface connected to the internet.

Let's see a diagram to understand how an IP Address is allocated to a device in a home or small network.

The router connecting the device to the internet generally has two network interfaces. These two interfaces are referred as:

• External Interface
• Internal Interface

A unique IP address is assigned to both the interface of the router. The IP address assigned to the internal interface is the internal IP Address. In contrast, the IP Address assigned to the router's external interface is known as the External IP Address. The External IP Address is routable and is usually assigned by your Internet Service Provider (ISP). This address is also known as a Public IP Address.

The External IP Address is ranged. The range determines the functioning of the device. The range of public addresses is assigned to the Internet Service Provider by Internet Assigned Numbers Authority (IANA).

A special range of Internal IP addresses is assigned for a home or home office network that uses a NAT router to connect to the internet.

NAT router is used to connect thousands of devices, such as computers, laptops, or mobile phones, all connected to an internal network in accessing the internet by using a single external IP Address to all the devices in the subnetwork.

A particular range of addresses is reserved for internal addresses . the routers on the internet do not share the IP addresses within this range. Therefore, internal addresses are also known as Private addresses. They are exclusive to a private network.

For example, all the devices at my home have an internal address in this format, 192.168.1.x, but the external address for the same device is 109.155.209.165.

The home networks have an address that ranges between 192.168.0.*-192.168.1.*. This network range is nonroutable. This range is only used for private addresses exclusively. This is one of many ranges that are used by home networks. They can also use the following address ranges:

10. x.x.x: This range provides a 24-bit block address.

172.16.x.x to 172.31.x.x: The given range provides a 20-bit block address.

Finding the External or Internal IP Address for the Device

Finding External Address

It is simpler to find the external IP address of the device. The external IP Address is routable and is available on the internet. You can find the IP address using a simple Google search query.

Just open the browser, and type my IP Address, and your IP will be displayed in the following manner.

1. 103.159.35.231  

This is your external IP address.

Finding an Internal IP address

Open the command and line in your system and write a simple command:

1. ipconfig  

The result will be displayed as follows:

Thus, the internal IP Address of your system is 192.168.1.64, which is different from the external IP Address of the device.

The internal IP Address is available to the local devices and network. The external IP Address is used to facilitate communication with the devices available on the internet.

Providing Access from the internet to the local network

It is not possible with a NAT router to establish a direct link between the internet and a device on the local network. So, any communication with the internet must be initiated by your device on the local network. This is not a problem, but it provides a solution to the security concerns associated with the internet.

However, the players who play online games, especially those that enable the user to play with other users online. The website that hosts these games provides Access to the external device on the internet. To provide Access to the external IP Address to the internet, the NAT router is configured using a method known as port forwarding. This technique allows the device on the local network to have an additional IP Address that allows the users to establish incoming connections from the internet.

Summary

In-home and small business networks, the network uses a private IP Address known as the internal IP address that is only visible to devices connected to the particular sub-network. This address lies in a special non routable address range.

A NAT router is responsible for establishing a connection between the internal network and the internet using the external IP address assigned to all the devices on a local network by the Internet Service Provider.

An external network can't connect with the local network unless the user employs techniques such as port forwarding. The NAT router enables the user to establish the connection initiated by the internal network to the external network.