Network Basics - Part 2(continue)

Public and Private IP Address

Both of these IP addresses exist to provide unique identification to every device on the network. 

Public IP address

• Public IP address is also known as an External IP address. 
• It is provided by your Internet Service Provider (ISP) and is assigned to your home network so that your home network gets a unique identification to the outside world. Any device on the network shall be able to communicate to your home network through this IP address. 
• It is unique throughout the internet. No 2 devices on the internet have the same public IP addresses. 
• It is further of 2 types, static IP address and dynamic IP address.If your ISP issued you a static IP address, then you will enter this IP address in your router’s network settings while setting up your router and that is going to serve as a unique identification for your home network to the internet. In case of dynamic IP address, you enter DHCP (Dynamic Host Configuration Protocol) in your router’s network setting while setting up your router. DHCP tells your router to accept the IP address issued by your ISP from time to time.

Private IP address

• It provides unique identification to all the devices within your network. It is also called as an internal IP address as it is assigned to the devices within your private space(inside your network). 
• Like public IP address issued by your ISP, router issues private IP addresses to all the devices within your network so as to provide unique identification to all devices within your network.
• Private IP address enables devices within your network to communicate with one another. The network configuration settings of each device in your network is stored on DHCP, so that it can accept the IP address issued to it by the router.

Note:

As private IP address is used for unique identification of devices within your network, it is never used outside your network. Similarly, your public IP address is never used within your network. Router controls network traffic within your home network and outside of it. Router ensures that data flows to correct the places.

Public & Private IP address

In the above example of home network, we have 2 personal computers as PC1 & PC2 and 1 network printer that are connected to a switch, which in turn connected to a router. We also have a laptop which is connected to the router (wireless connectivity). All these devices - PC1, PC2, network printer, switch and laptop that are connoted to router gets a private IP address from the router via DHCP protocol, whereas router gets a public IP address issued by ISP.