The internet has slowly grown to become an essential aspect of everyday life. Often, we take advantage of its resourcefulness without the curiosity to understand how things work. But if you are even slightly curious, you must have come across the term IP address.
Simply put, IP addresses facilitate communication over the internet (we will detail how that works in later sections).
However, not all IP addresses perform the same function, as some have special functions. 127.0.0.1 is an example of such an IP address. Read on as we look into this localhost address and understand how its function differs from other IP addresses.
What Is an IP Address?
To make it easier to understand what a localhost address is, we first have to understand what is an IP address and how it works.
An Internet Protocol (IP) address is a string of 32-bit (IPV4) or 128-bit (IPV6) characters that identify devices connected to a computer network or devices on the internet (which is also a network).
The role of IP addresses is to ensure information gets to the correct destination when transmitted over the internet.
In comparison, just like you need an address to send and receive mail and to ensure your mail does not get lost, internet devices require IP addresses to send and receive data.
IP addresses consist of numbers ranging from 0 to 255 but are written in a specific format, i.e., 192.0.2.1 for IPV4 and 2001:db8:0:1234:0:567:8:1 for IPV6.
There are two versions of IP addresses, i.e., IPV4 and IPV6. IPV4 came first hence why IPV4 addresses are more prevalent. There was a need for more IP addresses, so IPV6 was launched to ensure the world does not run out of IP addresses considering the steady increase of internet devices.
The two major functions of an IP address are location addressing and identifying the host or network interface.
Since we are concerned with the localhost address 127.0.0.1, we will focus on IPV4 addresses.
IPV4 addresses are written in the format X.X.X.X. X is called an octet and represents a value between 0 and 255. There should be four octets separated by three periods in an IPV4 address.
Notably, not all IP addresses are available for general use. Instead, they are classified into various classes that specify what role each range of IP addresses is supposed to play.
In these classes, there are IP addresses with specified roles; for instance, the range 127.0.0.0/8 (127.0.0.0 – 127.255.255.255) is known as the loopback range and is used by systems to ping themselves.
These classifications and allocations of IP addresses are handled by the Internet Assigned Numbers Authority (IANA) and the Internet Engineering Taskforce (IETF)
IP Addressing Basics
What Is 127.0.0.1?
The IP address range 127.0.0.0/8 (127.0.0.0 – 127.255.255.255) is known as the loopback range.
It gets this name from the special function these IP addresses are meant to play.
IP addresses in this range are on the same operating system sending an inquiry. Therefore, when a system pings IP addresses from this range, we would say it is pinging itself.
The primary necessity for this feature is that programmers can test their systems or websites without going through the internet.
Additionally, the IP addresses in this range are private, meaning they do not connect to the internet. Instead, they are meant to work within a local network; in other words, they are non-routable addresses.
Notably, the IP address 127.0.0.1 is the one that is typically used by systems to ping themselves.
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If data packets are sent from a system through this IP and the receiving system analyses the source and return address of said packets, it will find that the packet came from itself. Think of it like sending yourself flowers.
So, when replying, the packet will be returned to the same system hence the name loopback address.
The TCP/IP’s link layer handles data packets on a loopback address. The data will only interact with the system, not its Network Integration Card, thus the internet.
Therefore, the address 127.0.0.1 is meant for a system to reply to the originating device, i.e., itself. In contrast, the other IP addresses in the range are used to communicate with network devices on the local network, for example, a web server.
If you ping the address 127.0.0.1 using the command prompt on your computer, it should respond, and if it does not, then there is a problem with its TCP/IP stack.
What Is Localhost?
If you conduct a little research, you will see that the term “localhost” appears in most places you see the 127.0.0.1 IP address.
There is no big difference between 127.0.0.1 and localhost since they both refer to your computer/system as the packet data source.
The difference is only in the naming because when you want your computer to ping or send data to itself, remembering the IP 127.0.0.1 might not be easy.
Therefore, instead of remembering the IP address of every page you want information from, you use a domain name.
Domain names are meant to make it easier for you to access information instead of remembering IP addresses which would be impossible.
The back-and-forth conversion of domain names to IP addresses is handled by the Domain Name System (DNS).
Therefore, you can use the address 127.0.0.1 or localhost, but some systems prefer one over the other.
What Are the Uses of Localhost/127.0.0.1?
There are various other uses for this IP address apart from those already mentioned. Additional uses include:
1. Conducting a Speed Test
You can use Loopback addresses to test the speed of local networks within an organization or at home.
When pinging localhost, you can also view the number of data packets sent, the time it took for them to make a round trip, and how many data packets were lost in the process.
The speed tests will let technicians know if any optimization is required or if the network is working as it should.
2. Blocking Websites
You can use the localhost feature to block malicious websites in all browsers on your computer.
You need to locate the host file on your system to do that. A host file contains IP addresses and their hostnames.
Therefore, you can block a website by changing its IP address to a localhost IP and thus redirect attempted access on your system to the localhost.
3. Test Websites and More
Web developers can test their website applications locally using the localhost. That way, they do not have to connect to the internet every time they want to conduct a test.
Therefore, a developer can host the website on a server and then access it using the localhost address. That enables one to test a website before making it available to the public.
You can also use Loopback addresses to access servers hosted on your local network.
Some games like Minecraft will allow you to host a server on your system and, in turn, let you play with friends.
Localhost/Loopback Address Explained
As we have seen, a localhost address is an essential feature, especially for programmers. The IP address helps cut programmers’ workload by testing websites and programs without connecting to the internet.
The fact that programmers use the IP address 127.0.0.1 to run tests on their devices (localhost) rather than over the internet gave rise to the phrase: There is no place like 127.0.0.1. A reference to the no place like home phrase.
Hey, I’m Jeremy Clifford. I hold a bachelor’s degree in information systems, and I’m a certified network specialist. I worked for several internet providers in LA, San Francisco, Sacramento, and Seattle over the past 21 years.
I worked as a customer service operator, field technician, network engineer, and network specialist. During my career in networking, I’ve come across numerous modems, gateways, routers, and other networking hardware. I’ve installed network equipment, fixed it, designed and administrated networks, etc.
Networking is my passion, and I’m eager to share everything I know with you. On this website, you can read my modem and router reviews, as well as various how-to guides designed to help you solve your network problems. I want to liberate you from the fear that most users feel when they have to deal with modem and router settings.
My favorite free-time activities are gaming, movie-watching, and cooking. I also enjoy fishing, although I’m not good at it. What I’m good at is annoying David when we are fishing together. Apparently, you’re not supposed to talk or laugh while fishing – it scares the fishes.