127.0.0.1 is a set of numbers that you may have heard a technician on the phone tell you to type on your computer screen. This odd number series is called a loopback address, which is also called the local host. These things may sound like very technical things but really they’re not. Add to that the interesting fact that computer terminology is quite descriptive.

Figuring Out the Definitions

Loopback simply means something that returns or goes back to its source. On the other hand an address is something tells us the location of someone or something. So, using a small amount of Sherlock Holmes deductive reasoning, a loopback address is an object that tells us the location of something that basically points to it. This address is also called the local host, which simply refers to the computer where the signals are coming from.

When computers are interconnected, there should be a way to identify, refer to, or address each computer. That way when one computer tries to communicate with anther computer on the network the computers can figure out which address to use.

Computers use a series of numbers to identify all the computers in a network. 127.0.0.1 in layman’s terms is simply the address that every computer in a network uses to refer to itself. This may sound a bit impractical for some who may also think that it has no practical use at all. But the fact is that it has practical uses other than helping a computer identify itself on a network.

How Does a Loopback Work Anyway?

A loopback address works very much like any address used to refer to any other computer in the network. One computer trying to communicate to another computer in the network will prepare data in the form of packets. You can think of them as packages that are contained in different compartments. Other than preparing packets, the computer also identifies the address of the receiving computer.

Both the data packets and the receiving computer’s address are forwarded to a routing device (such as a router or a switch), well at least that’s the case for the usual communications between computers. In the case of 127.0.0.1 the local host is expected to respond to the said piece of communication. In case a packet slips with a loopback address and somehow gets to the router then it is automatically dropped.

What Practical Use Could That Bring?

One quick answer – testing. For instance, a user can issue a ping command to test the IP stack of the computer he is using. If the ping executes without any problems then the functionality of the IP stack is determined. This is actually one of the most basic uses of 217.0.0.1.

In order to execute this ping command, in case you want to try it yourself, open a command screen by typing ‘CMD’ on the Run window (executed by pressing the Windows button + R) and hitting Enter. A command prompt window will open. At the prompt, type “ping 127.0.0.1” then hit Enter. Four packets will be sent and four packets should return as replies. If the ping statistics report a 0% loss then the IP stack should be working fine.

Note that this does not actually mean that the network interface card is working. You need to do a different set of troubleshooting to check your computer’s NIC. If your ISP’s support technician tells you over the phone that the network interface card is okay when a ping to the local host or loopback address is successful, you can tell him he’s mistaken.

Other than doing ping tests, there are other types of testing that can be done using this address. Another form of testing occurs when a client software program uses it to communicate with a web server application that is also installed on the same computer. This is a very safe way to test the functionality of a computer’s services minus any possible external threats that may be present in the network.

These are the useful applications of 127.0.0.1. It’s a very useful tool for testing your computer system. Now you’re prepped for slightly better times ahead next time you call technical support.

Charlie is a free lancer writer and content builder of many Technology sites sites and he is explaining this IP address 127.0.0.1