A local host, also called a loopback address, is used to establish an IP connection or call your own computer or machine. The loopback address is usually used in the context of a network and allows the computer to inspect the IP stack.
Anyone with a background in or interested in networking will find it important to learn and understand related computer terminology in this area. Localhost is one such term that is useful to any computer professional. Understanding the importance and use of localhost is also a great start to familiarizing yourself with networking terminology.
What is localhost and how is it used?
The required address will depend on the internet protocol used. A call to localhost using IPv4, which is the most common IP address, will have a range of 127.0.0.0 to 127.255.255.255, but will usually default to 127.0.0.1. IPv6 users can set up a loop by entering: 1.
The Internet Protocol (IP) was introduced to establish a standard method for computers to communicate with other devices on a network. It not only manages addresses, but also how your data is sent and received both on local networks and on the Internet.
IPv4, which is Internet Protocol Version 4, is the most widely used worldwide. IPv4 relies heavily on the Transmission Control Protocol (TCP) to handle large amounts of data such as delivery, consistency, and integrity. This IP address was designed as a connectionless protocol for use on Ethernet machines.
IPv6 began to gradually replace IPv4. The demand for IP addresses has grown exponentially since the digital boom. More and more devices use the Internet, so IPv6 was designed to increase and address some of the fundamental flaws found in IPv4.
Whereas IPv4 allows approximately 4.3 billion unique IP addresses, IPv6 allows up to 340 trillion trillion.
Besides numbers, IPv6 also offers networking benefits. This simplifies discovery between devices on other IPv6-enabled networks, allowing users to consume services without requiring end-user action. Using IPv6 also greatly reduces the need for Network Address Translation (NAT). NAT allows IPv4 clients to share a single IP address.
Since IPv4 is the most common of the two Internet protocols in use, we will pay more attention to it later on.
How does 127.0.0.1 work
When you establish an IPv4 connection with a loopback address of 127.0.0.1, a subnet mask of 255.0.0.1 is assigned. This way, if any public switch, router or gateway receives a data packet with your feedback as a destination, no data information will be logged.
This means that if a data packet is dropped outside the local host, the information will not be transferred to another computer on the network. This helps maintain network security by preventing your computer from receiving random packets of data that might try to activate other services in response.
Localhost Common Uses
Besides security features, localhost can be useful in several other scenarios. There are three main purposes of the loopback address, which are considered useful by the computer network specialist.
Running a speed test
Sending a ping request is the most common use of the loopback address. Using the Windows Command Prompt, you can test the connection and detect any performance issues your computer may currently be experiencing.
To ping localhost:
- Open the Run dialog (Windows key + R) and type cmd. Hit Enter.
- You can also type cmd into the search box on the taskbar and select a command line from the list.
- It is recommended to run as administrator.
- Type ping 127.0.0.1 and press Enter.
The results will be displayed on the screen. The data displayed will include the number of data packets sent, received, lost, and the estimated round trip time.
When you need to block access to certain websites, localhost can help. The loop can be quite useful in preventing malicious sites from penetrating your browser. To do this, you need to know what host files are and what they serve in this context.
Every time your computer tries to access a website or a remote computer using a domain name, the computer will send a query to a Domain Name System (DNS) server looking for a locally saved host file.
For example, the IPv4 address 127.0.0.1 will appear in DNS as “localhost”. The domain name of any new website you visit will also be saved as a host file. This speeds up loading on repeat visits to the same site.
The host file will also contain the IP addresses of all domain names that it stores. You will have to edit these IPs to match the loopback address 127.0.0.1 in order to block them. Instead, traffic will be directed back to the local host.
While it works as a last resort, using localhost as a method to prevent access to unwanted websites is not the best solution. The main reason is that if you need access to these sites, you will have to manually delete the entry as an administrator. Only the administrator who created the original entry can do this by blocking everyone who, for one reason or another, needs to access a particular site.
Testing new programs or web applications
Every time a loop starts, your operating system becomes a simulated server. This allows you to upload any necessary program files to the server for a functional check.
When combined with other software, you can even use loopback to allow side-loaded mobile apps to access desktop server components or send requests to a specific API.