Why loopback interface is used

I want to have two different paths available with one IP address so that I can use those two different paths to get to R1. I'll go to the global configuration mode in R1 and configure the loopback interface. The command in creating loopback interface is:. The number can be anything that you want to use, in this lab, I used zero.

That creates the interface and it takes you to the configuration mode for the interface as well. Notice that the interface goes up immediately because it is a loopback. There is NO need to perform a no shutdown command. I also need to make sure that it's being advertised in my routing protocol so I'll execute the command:. Therefore, to include the loopback address, I will enter the commands:. Let's see if the route is there using the show ip route command.

There are two paths, but one of them has got a better cost. I can ping This is important for troubleshooting it can be compared to looking in a mirror. The loopback device is sometimes explained as purely a diagnostic tool. But it is also helpful when a server offering a resource you need is running on your own machine. For example, if you run a web server, you have all your web documents and could examine them file by file.

You may be able to load the files in your browser too, though with server-side active content, it won't work the way it does when someone accesses it normally. So if you want to experience the same site others do, the best course is usually to connect to your own server. The loopback interface facilitates that. For IPv4 , the loopback interface is assigned all the IPs in the That is, For most purposes, though, it is only necessary to use one IP address, and that is This IP has the hostname of localhost mapped to it.

Like other network adapters, the loopback device shows up in the output of ifconfig. Its name is lo. One common, production i. In a web browser, go to:. All the If you come from a Windows background, you might expect loopback to itself be a synonym of localhost and thus to be able to ping loopback , connect to servers on loopback , and so forth. That behavior is peculiar to Windows. The general concept of loopback is a mechanism through which a message or signal ends up or loops back to where it started.

So there are a few other ways loopback is use in Ubuntu that should not be confused with the loopback device in networking. This is usually called a loop device and not a loopback device , but the term loopback file interface is occasionally used.

Because the loopback interface is always up, you ensure that the switch's router ID remains constant and that the OSPF network is protected from changes caused by downed interfaces. The disadvantage is that if the interface goes down, OSPF can no longer ping the switch using the router ID even if other interfaces are operational.

To configure a loopback interface, enter the interface loopback command at the global configuration level of the CLI:. Use the no form of the command to remove the loopback interface. Note: You cannot remove the default loopback interface number 0 with IP address You can configure up to thirty-two IP addresses on a loopback interface. Note that when you configure an IP address for a loopback interface, you do not specify a network mask. The default subnet mask We can overcome this issue by configuring a loopback interface.

The IP address assigned and advertised over the network, the loopback interface is used to communicate with the router whose interfaces are down. Loopback interfaces are automatically turned on immediately after configuring the interface on a router. We can also use the ping command to verify if a router IP stacks working properly. The loopback address is used to access the router for management. They help to select, designated router and Backup Designated router when the routing protocol OSPF is configured in the network.

Loopback interfaces can establish a telnet session from router console port to the auxiliary port when all physical interfaces are down. This loopback interface helps an administrator to determine if the interface configured is working properly or not. Loopback line helps the administrator to find out if there is a problem from the service provider end.