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Public vs. Private IP Addresses

Last Updated: Fri, 22 Apr 2011 > Related Articles

Summary

What's the difference between a public and a private IP address? Learn here.

Solution

 

A Public IP Address is a globally unique number that identifies a device on the Internet. If you want someone on the Internet to connect to you, then you must tell them your public address. Also known as your “real” or “external” address. Public IP addresses are globally recognized and assigned by the Arin. Arin is the governing body that controls the list of publicly routed IP addresses. Your ISP usually gives you a public IP.

A Private IP Address is typically assigned to devices on a LAN (Local Area Network) and are not used outside the LAN. These IP addresses are typically used with a router, where you have multiple computers all sharing the same Internet connection. Private IP addresses cannot be used on the internet.

Private addresses are often used for isolated, IP-based networks that will not be connected to the public Internet. InterNIC encourages the use of private addresses for these situations because it reduces the waste of public IP addresses.
However, when using NAT (network address translation), you can have private IP addresses on your local network and use a single public IP address to have them access the internet. Using NAT, you would be able to connect hundreds of computer to your router, and then use one public IP for all computers to access the internet. A router will translate between private and public IP addresses.

 

 


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