What are the differences between private IP addresses and public IP addresses? How a private IP network is mapped to a single public IP?

Private IP addresses are IP addresses reserved for building private networks within an organization. Private IP addresses are listed below:

Class   Private IP Range
-----   ------------------------------
A       10.0.0.0 to 10.255.255.255
B       172.16.0.0 to 172.31.255.255
C       192.168.0.0 to 192.168.255.255

Public IP addresses are IP addresses reserved for building the public Internet. Any non-private IP addresses are public addresses. Public IP addresses are managed by different Internet administrative organization. If you want to reserve some public IP addresses for your organization, you have to get them through your ISP.

When connecting your private local network to the public Internet, you ISP will assign a dynamic or static public IP address to represent your entire private network. In order for all local devices to share the same public IP address when communicating to a remote host on the Internet, you need a NAT router to perform NAT (Network Address Translation) tasks.

Fortunately, today's WiFi routers can also perform NAT tasks, so you don't need to buy any additional hardware.

Here is an example of WiFi router performing NAT tasks to allow a private local network (192.1.68.0.0/24) joining the public Internet with a single public IP of 82.10.250.19.

⇒ NAT Algorithm and Connection Tracking Table

⇐ What Is IP Routing

⇑ IP Network

⇑⇑ Internet Connection - Frequently Asked Questions