Why 127.0.0.1 is loopback

But this is not the case in IPv6? IPv6 has link-local addressing. Not the same thing, but applicable. Mark Henderson Mark Henderson Also keep in mind that it's IPv4; there were three revisions before the final and they kept some of the cruft for compatibility reasons. LawrenceC LawrenceC 1, 6 6 silver badges 14 14 bronze badges. The fact that this does not occur in any other address was used as an optimization, not because they thought it made sense to reserve 16 million loopback addresses it didn't, and still doesn't.

Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. This document explains how to configure a default route or gateway of last resort. These IP commands are used:. Creating a static route to the network 0. As with the ip default-network command, using the static route to 0. However, IP routing must be enabled on the router.

Note: IGRP does not understand a route to 0. Therefore, it cannot propagate default routes created using the ip route 0. Use the ip default-network command to have IGRP propagate a default route. Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here. Browse All iPhone Articles Browse All Mac Articles Do I need one?

Browse All Android Articles Browse All Smart Home Articles Customize the Taskbar in Windows Browse All Microsoft Office Articles What Is svchost. Browse All Privacy and Security Articles Browse All Linux Articles Browse All Buying Guides. Best iPhone 13 Pro Case. Best Bluetooth Headphones for Switch. Best Roku TV. Internet Protocol version 4 or IPv4 is the fourth revision of the protocol and is the most widely deployed throughout the world.

IPv4 is considered to be a connectionless protocol designed to be used on Ethernet-based networks. The protocol does not guarantee delivery, data integrity, or proper data sequencing; instead, relying on the Transmission Control Protocol TCP to handle these concerns. Establishing a network connection to the The primary difference is that the connection avoids using the local network interface hardware.

System administrators and application developers commonly use When establishing an IPv4 connection with If any public switch, router, or gateway receives a packet addressed to the loopback IP address, it is required to drop the packet without logging the information. As a result, if a data packet is delivered outside of the localhost, by design it will not accidently arrive at a computer which will try to answer it.

This aspect of the loopback helps ensure network security is maintained, since most computers will answer packets addressed to their respective loopback address which may also unexpectedly activate other services on a machine by responding to a stray data packet. Human beings are not able to easily remember IP addresses or number well.

Plain language web addresses; however, are much easier to use, but require a method to resolve to the actual address of the remote computer or server. As a result, the Domain Name System DNS , was developed to help direct local and Internet traffic to the appropriate destination by performing real-time look-ups of Internet address with other DNS servers located on the Internet.

Before a local computer will send a DNS request to the DNS server for the local network; however, it will perform a check of the locally stored Hosts file first to save time and network resources. The hosts file contains pairings of IP addresses along with one or more host names and is updated frequently based on predefined conditions on the local computer.

Before the invention of DNS, there was a single Hosts file that was shared across the network. This was found to not pass the test of scalability; however, when multiple networks started to get connected together which resulted in the development of the DNS system in use today. Whenever a computer user tries to access a website or remote computer by name, the computer checks the locally stored Hosts file for domain name resolution before sending a request to the Domain Name Server DNS.

The This type of change has most commonly been associated with many of the computer scareware packages that have been deployed across the Internet through maliciously infected websites, Trojan horse viruses, and infected email attachments. Some computer administrators, and interested students, can modify the hosts file to prevent access to undesirable websites; however, is not the preferred method as the end-user or administrator now becomes responsible for removing the entry when required.

Examples of host file entries:. RFC was the first specification to collect the various one-off definitions for special use IP addresses such as Based on these lessons learned, all of the special user IPv6 addresses were included in RFC from the beginning. People studying computer networking sometimes confuse While both have special meanings in IPv4, 0.

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