IP Addresses

In order to send and direct data across a network, computers need to be able to identify destinations and origins. This identification is an IP—Internet Protocol—address. An IP address is just a set of four numbers between 1 and 254, separated by dots. An example of an IP address is 173.194.43.7.

An IP address is similar to a street address. Parts of the address describe where in the world the building is located, another part narrows it down to a state or city, then the area within that state or city, then the location on the street.

Below we can see 192.168.1 Street. On it are three houses:

The complete addresses for each of these houses is: 192.168.1.20, 192.168.1.21, and 192.168.1.22.

There are different classifications, or types of IP addresses. A network can be public, or it can be private. Public IP addresses are accessible anywhere on the Internet. Private IP addresses are not, and most are typically hidden behind a device with a public IP address.

Here we can see an example—a street with two buildings with public IP addresses—representing computers with addresses that are visible to the entire Internet. These buildings might be anywhere in the world, but their addresses are complete, so we know exactly where they are and can send messages to them.

To see an example of how public and private IP addresses are commonly used, let’s take another look at 192.168.1 Street. We have a new building on the street. That building has a public IP address, and a private IP address. There is also a fence that blocks the rest of the Internet from seeing and passing messages to addresses on the street.

The postal building controls messages that travel between the Internet and the street, keeping track of messages that leave the street, and directs return messages to the right house. On the street, it has the address 192.168.1.1, and on the Internet it has the address 74.10.10.50.

Activity: Find the IP addresses assigned to your computer, and your network.

What is the IP address for your computer? ____________________


Browse to http://ip.mayfirst.org/ 
and write down the IP address it reports: ____________________

Are these numbers the same, or different? Why?